The head chef of Épure in Hong Kong, located at Ocean Centre in Harbour City, since 2013 and the proud holder of a Michelin star since 2017, Nicolas Boutin sheds light on the authenticity of French products through his original, precise and tasty cuisine. It's in this spirit that he created his famed signature dish: sweet onion of Cévennes with black truffle (oignons doux des Cévennes à la truffe noire). Here, Boutin shares this recipe exclusively and for the first time with CDLP.

What is the origin of  this recipe?

Well, I wanted my cuisine to become increasingly minimalist, so I created recipes with products that are little used or misused in traditional dishes in order to sublimate them. I had been thinking of this recipe over the course of two or three years. My team and I ended up doing tests with different varieties of onions, and gradually we arrived at the result that we have today.

Three years of testing?

I had been thinking about creating a recipe based on onions, an ingredient rarely presented on its own, for a long time. During those two to three years, I took the time to test ideas, but also to take breaks from the project for it to mature. It's like this for every recipe. The process is similar to the one of a music composer or an author…

The onion is a rather commonplace vegetable – why associate it with something as high-class as truffles?

As with any vegetable, there are different varieties of each product – and this is also true for onions. We had to find an onion – and not the basic yellow onion most commonly used to make sauces or to cook. As the chef of a French restaurant, the idea was to find a variety of French onion, either Roscoff or Cévennes. After many trials, I chose the Cévennes onion. I managed to reach a certain texture that's neither overcooked nor undercooked, which retains its crunch and sweetness. The idea of the truffles came quite naturally because of the season in which I started to think about this recipe.

Which variety of truffle should one use for this dish?

You need fresh black winter melanosporum truffle – it is very important for the taste. Depending on the season, it can come from either France or Australia. We did some tests with summer and autumn truffles, but this was of no use because those truffles have little to no taste. If one cannot find fresh truffle, I suggest using frozen or canned black winter melanosporum truffles.

Sweet Onion of Cévennes with Black Truffle

• 1 medium-sized sweet onion from Cévennes (or, failing that, a white sweet onion)

• 1 black melanosporum truffle (12–15g)

For the sauce:

• ½ large shallot, very finely chopped

• 100ml chicken juice 

• 20g butter

• 1 tbsp port wine

• ½ tbsp powdered sugar

For the tile:

• 30g spelt or buckwheat flour

• 140ml grapeseed oil

• 140ml water

• 140ml chicken broth

How is this recipe prepared? 

There are several important steps. First, the whole onion is cooked, unpeeled, on a bed of coarse salt in the oven at 160°C for more than an hour and a half. This renders the onion tender without being overcooked. It's then left to cool before being peeled. The next step is to cut the onion in half, separate each leaf and spread them individually. On each slice, a little olive oil is brushed, then a little piment d'Espelette chilli powder is added – to replace the pepper – and finally, a slice of black truffle is placed.

Simultaneously, a caramelised shallot purée and truffle meat juice are prepared. The minced shallots are fried in an anti-adhesive frying pan, with a little butter and sugar to caramelise them before being blended. Finally, the meat juice (preferably chicken) and truffle pieces are added before being blended as well. We then recreate each half of the onion. For the layers to be held together, we prick each half of the reconstituted onion.

When the order for the dish is placed, we slightly roast the truffle onion – and we add a "tile" that is made with spelt or buckwheat flour, mixed with a little water and a little oil. It is cooked in the pan that was used to caramelise the onion for one to two minutes. This tile will bring the crispness to the dish. The onion is then ready to be placed on top of the plate.