What about the idea of cooking onions under salt, a fantastic way to preserve flavour, and control humidity and temperature. Perhaps one of the oldest tricks in the book, smothering a vegetable or meat under a cavity to contain the heat and distribution of moisture temperature.

One day in late fall, I was visiting Cesare Giaccone and he served brought a whole onion roasted to a deep mahogany color. On closer inspection it becomes obvious that these onions are stuffed with a bechamel flavored Parmesan and stuffed in the interior of the roasted onion.

http://mesubim.com/2013/11/17/cesare-cesare-part-1/
http://mesubim.com/2013/11/18/cesare-cesare-part-2/

Recipe Ingredients

Rock salt

8 small to medium white onions
1/4 cup butter
1/4 cup flour
1 cup milk
1 1/4 cups freshly grated Parmigiano Reggiano
1/4 teaspoon salt
1/4 teaspoon white pepper
1/4 cup vegetable stock
Freshly grated nutmeg

Pour rock salt one inch deep into baking pan large enough to hold all onions. Peel onions, leaving roots intact, and arrange, root-side up, on top of rock salt. Bake at 175°C until onions are soft and this takes approximately 90 minutes.

Melt the butter in small saucepan ans add flour and mix to make smooth paste. Cook, stirring, until flour is light tan which happens in 5 minutes. Add milk and cook, stirring, until sauce thickens, about 5 minutes.

Whisk in 3/4 cup freshly grated Parmigiano Reggiano. The mixture should be quite thick and will thin when the pureed onion is added.

Season with salt, white pepper and nutmeg and continue cooking at least 30 minutes over very low heat, stirring occasionally to keep it from getting scorched.

When onions are soft, remove from oven and cut small slice from root end. Scoop out insides of onion, leaving just shell intact.

Puree the insides in a food processor along with some vegetable stock. Stir onion puree into cheese mixture and whisk to combine it and adjust seasoning.

Fill onions with cheese-onion mixture and top each onion with some grated Parmigiano Reggiano to form long strands. These will form trompe l’oeil “roots” when browned.

Place onions back in same baking pan on top of rock salt and continue baking at 175°C until browned for 5-10 minutes and then reduce heat to keep warm.