This is quick to make, delicious, and really versatile. I love eating them hot over grilled polenta, or as a snack on toast. I’ve even used them to make lasagna. They also make a... wonderful appetizer.
Heat the olive oil over a medium high flame in a wide sauté pan. Add the thyme and the garlic, and cook stirring for 1 minute. Add the shallots and cook stirring until the shallots start to color, about 5 minutes.
Add the mushrooms and salt to taste. Cook stirring until they start to loose their water, about 5-8 minutes.
Stir in the mosto cotto and cook, stirring until it just starts to evaporate. Cover the pan and turn the heat down to low. Simmer for 10 minutes. Check to see if there is enough liquid - the mushrooms should sit in a syrupy sauce. Turn the heat off and let the mushrooms sit covered for 5-10 minutes to finish cooking.
Serve hot as a side, or at room temperature as an appetizer.
Mosto cotto is a syrupy reduction of balsamic vinegar. If you can’t find Saba, or another ‘mosto cotto’, use ⅓ cup balsamic vinegar and 1 teaspoon sugar.
When you buy Portabella mushrooms, look for caps that are dry, with undersides that are velvety and a light taupe in color. They should have a light mushroomy scent. If you see any black wet patches on the undersides, or the mushrooms smell dank or sour, they are old.