Prepare the ingredients: use half the onion for a bouquet garni, and finely chop the remaining 1/4 onion and the 2 garlic cloves.

Make a béchamel sauce. In a skillet, melt 2 tablespoons (about 1 oz or 30 grams) of butter. Once melted, add the flour to make a roux.

Add 1 2/3 cups (about 400 ml) of milk and the bouquet garni, season with salt and pepper, and let it thicken.

In a pot, melt the remaining 2 tablespoons (about 1 oz or 30 grams) of butter and caramelize the chopped onion and garlic. Add the huitlacoche and 2 pinches of salt to enhance the aroma. Cook for about 10 minutes.

Transfer the béchamel sauce and huitlacoche mixture to a blender and blend until very smooth.

In the same pot used for the huitlacoche, sauté the mixture to preserve the aroma. Add the olive oil. Stir in the heavy cream and the remaining 1/3 cup (about 100 ml) of milk.

Let it thicken, then serve.