2 tablespoons extra-virgin olive oil
1 tablespoon unsalted butter
1 ½ cups chopped onions
1 tablespoon sugar
4 ounces goat cheese, softened
1 large egg
2 tablespoons heavy cream
1 teaspoon fresh thyme leaves
1 (14-ounce) box refrigerated piecrust
Salt, to taste
In a large heavy-bottomed skillet over medium heat, add the oil and butter. When the butter is melted, add the onions, sugar, and salt to taste. Cook until the onions begin to brown. Turn the heat to low and cook slowly, turning often, until the onions are golden brown and caramelized, about 12 minutes. Remove from the heat and set aside to cool.
Preheat the oven to 375°F.
In a bowl, mix together the goat cheese, egg, cream, and thyme. Pour mixture into a plastic food-storage bag. Snip off a corner of the bag to use it for piping.
Lay a piecrust out flat, and with a 2 ½ -inch round cutter cut out 12 circles. Press them into the cups of a 12-count nonstick minimuffin tin. Fill each cup halfway with the cooled onions. Pipe the cheese mixture on top of the onions, filling up the cups. Bake the tarts until the filling is set, about 15 to 20 minutes. Let cool, then remove them from the muffin tin and serve.