© 2018 Can Caramelo

Quiche with Asparagus, Caramelized Onions, Dried Tomatoes & Black Olives

The other day a reader of my blog told me how interesting she found my posts about neuroscience and that she had been wondering about how it comes that we start to salivate just by imagining food we like or how we immediately crave something by perceiving the smell of it. She also wondered why we sometimes like the smell and even the flavour of certain food, but then are repelled by its texture. Before we get to these interesting questions, let’s agree on some fundamentals. While writing I realized this post was getting very long, so in this post I will explain a bit about how smell and flavour work and I will actually answer the questions in the next post. I did a little poll on instagram to see if people know how our brain mainly creates flavour – the question was if the input comes mainly from receptors in our mouth or (retronasal) smell. Although many people saw the poll, not so many answered, I guess many weren’t sure about the options. The answers were exactly 50% for each option. So let’s start from here.

Receptors in our mouth are actually only capable of tasting sweet, bitter, sour and salty. Plus, of course there is thermal sensation and texture. Spicy is actually something codified by receptors for pain. Even the touch of food if we eat it with our hands, the sound of biting into it and of course its visual aspect, influence flavour. But if you have a bad cold and your nose is stuffed, and you decide to eat an ice cream, you actually wouldn’t be able to tell strawberry from mango or coconut (eyes closed!).

So flavour comes mainly from retronasal smell. Retronasal means that we get the sensation of tasting something when we exhale while we have it in our mouth when eating. The perception of retronasal smell is closely linked to taste and touch, and as it all happens in the mouth, our perception fools us into thinking flavour comes form the mouth.

My parents told me early on that flavour mainly came from retronasal smell, and I’ve actually used this info as a trick as long as I can remember. I’m able to shut my nose innerly and thus avoid tasting or smelling something I don’t like. I remember being at a friend’s place as a little girl where her very strict mom used to make this quiche with vegetables which I hated at that time. By shutting out my sense of smell I could eat it without throwing up. Now when Simón poops in the potty I use it to avoid smelling the results.

To summarize, there is normal (also called orthonasal) smell, which refers to the odours we identify when breathing in air through the nose. This is what we commonly think of when we asked what smell is. But there is also retronasal smell, much less acknowledged, even though it’s the main component of flavour. Flavour can be be understood as an interplay between taste (as in bitter, sour, sweet and salty, which are identified by receptors in the mouth), touch -thermal sensation, spiciness, texture- vision, audition and smell (both orthonasal, when we smell food before putting in into our mouth and retronasal, when we exhale while the food is in our mouth).

Now that we agree on smell as the main component of flavour, let’s get a bit further into the details of how smell works. How do we identify the smell of a lemon or of a croissant? Volatile molecules from food reach receptor molecules in our nose. The smell pathway has very few relay stations: the olfactory bulb, the olfactory cortex and the prefrontal cortex.

While the representation of smells in the olfactory bulb is driven by stimulus properties, the representation in the olfactory cortex is memory based. So while the stimulus characteristics are represented in the olfactory bulb, the representation at the olfactory cortex is more abstract and depends on several factors. For instance, it adapts its response with prolonged exposure. I guess you have all experienced being really bothered by a strong smell and then not longer perceive it after a while. The cortex is also capable of learning, so that with repeated exposure the responses are amplified and contrasts are enhanced, this way a finer distinction becomes possible. It also improves the ability to match smell patterns with those stored in memory.

It’s also in the olfactory cortex where from the different smell components, a coherent smell object is constructed (like a croissant). This is analog to a visual object. Now, to make sense of this information, to consciously perceive a smell, the neocortex is needed. For all our other senses, before the cortex, information passes through the thalamus, a subcortical structure that has sometimes been called the “gateway to the neocortex”.

Smell is privileged. While a few fibers are send from the olfactory bulb to the thalamus, smell representations mainly go directly to the orbitofrontal cortex, one of the most developed parts of the brain in humans when compared with other animals. That means that information from the volatile molecules released when eating is so important that it is directly evaluated at the highest level in the human brain.

If you have any doubts, want to know anything else or if you’re really interested in how something specific works in our brain, let me know in the comments! I’ll be back soon with the second part of this post about flavour and our brain and a new recipe. For now, activate all your senses to experience this quiche with green asparagus, caramelized onions, dried tomatoes, kalamata olives and cheese.


For the crust:

  • 2 cups light or whole spelt flour (I used a mixture here, but I have used both with success)
  • 80g/2.8oz cold butter
  • 1 egg
  • 1 teaspoon salt

For the filling:

  • 1 large onion
  • 6 eggs
  • 1 bunch green asparagus
  • 1/4 cup (plant) milk
  • sea salt & freshly ground black pepper
  • 100g cheese (I used a manchego style sheep cheese here, but you cut use goat cheese or similar as well)
  • 80g/2.8oz semi-dry or dried tomatoes in oil
  • 10-12 black olives, pitted (kalamata are my favorite)
  • 2 sprigs of fresh thyme
  • 1 tablespoon olive oil


Start with the crust. Put the flour in a large bowl and make a little mold in the middle. Add in the egg, salt, and the butter, cut into pieces. Mix quickly with your hands or a dough scraper, until just combined and you can form a ball. Cover the bowl and put into the fridge while you prepare the filling. Trim the ends (not the tips of course!) of the asparagus, add the olive oil to a pan and fry for a few minutes (5min or so) at medium-high temperature. Sprinkle with a little sea salt and reserve. Use the same pan to caramelize your onion. Finely slice the onion and add it to the pan. Fry at high temperature for around 5-10 minutes, stirring every now and then to avoid burning. Add 1/2 teaspoon sea salt and lower the temperature to medium and sautée for 5 more minutes.

Preheat the oven to 180ºC/350ºF. Pit the olives and cut in half. Pick the leaves from the thyme (or finely chop if it is very tender). Prepare your crust. I always use parchment paper below and on top to roll it out. Roll out into circular shape, you can cut of pieces and paste them where needed. An easy option is to put it into the pan with parchment below, that makes it super easy to both put and remove. Another option is to peel off the top parchment paper (if the dough sticks to it, refrigerate for 5-10minutes so that the butter hardens, afterwards it should be easy to remove) and use the bottom parchment paper to move the dough to the pan, flip it over and into the pan and then peel it off. Make a fluted edge or cut off overlapping dough. Cut the cheese into the desired shape. Crack the eggs into a large bowl. Beat until doubled in volume. Add the plant milk, thyme, salt and pepper. Put the caramelized onion on the crust. Top with the egg mixture. Add the asparagus, dried tomatoes, olives and cheese. If you have dough leftovers you can use them to decorate. Bake for around 40 minutes (the top should be browned and the center set). It can be eaten both hot and cold. It holds its shape well, but more so when not fresh out of the oven.

One Comment

  1. Lola
    Posted 24 Jul ’18 at 1:12 am | #

    Whoooo~! Can Caramelo ist zurück! Ich habe mich riesig drauf gefreut, wieder Geschichten und Rezepte aus meinem spanischen Lieblingshaus zu hören. Wie superduper cool (auch wenn ich etwas spät bin)! Die ganzen Fachwörter über unser Gehirn verwirren mich zwar etwas, allerdings ist das ein guter Moment, um etwas mehr darüber zu lernen. Ich bin gespannt wie’s weitergeht…

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