Peel the garlic cloves and cut them into thin slices.

Place the garlic in a heated pot of olive oil on low heat. Cook for about ten to fifteen minutes, stirring occasionally, until toasty brown.

Remove and drain on clean paper towels. Reserve the oil.

Remove the bottom of the stem of the mushrooms and cut into slices. Place the mushrooms in the reserved oil.

Sauté the mushrooms for twenty-five minutes, then add half of the salt.

Reserve a fifth of the mushrooms for garnish.

Add the onions to the mushrooms and cook until translucent.

Next, add the dry sherry, thyme sprigs, and remaining salt to the pot. 

Add the stock to the pot, reserving 1/2 cup to combine with the cornstarch. Add the cornstarch mixture to the pot and simmer for 20 minutes, stirring occasionally. 

Remove the thyme sprigs and puree the mixture.

Drain through a fine mesh sieve and return to the pot.

Mix in the heavy cream (omit if vegan) and return to heat or if eating cold, place in the refrigerator. 

Garnish with reserved mushrooms and toasted slices of garlic.