ONION AND SAGE TARTS

Steps:

• 1. Caramelizing the onions. Peel the onions and cut them in half from root to tip. Cut out the dense core at the root end and slice the onions 1/4 inch thick, again from root end to tip. Cook the bacon, stirring often, in a large (4-quart) saucepan over medium heat until almost crisp. Add the onions, sugar, and salt, and cook, stirring often until they cook down by two-thirds, about 10 minutes. Add 2 teaspoons vinegar, reduce the heat to medium-low, and continue to cook until the onions are an even golden brown and softened to a marmalade consistency, 15 to 30 minutes, depending on the onions. Stir often and scrape up any brown bits clinging to the bottom of the pan. The onions need almost constant stirring near the end to prevent them from sticking and burning. They'll let you know they need attention by giving off a sizzling sound. Stir in the sage, allow them to cool slightly, then taste and season with black pepper and additional salt if needed. If the onions seem overly sweet, stir in another teaspoon of vinegar. (The onions can be caramelized up to 2 days ahead and store covered in the refrigerator.)
• 2. Filling and baking. Preheat the oven to 350°F. Stir the cream and egg into the caramelized onions until thoroughly combined. Divide the filling among the tart shells and spread it evenly with the back of a spoon. Bake in the upper third of the oven until the filling is set, about 15 minutes. The filling should still be soft but not runny. Let cool slightly, then transfer the tarts to a cutting board using a large spatula. Cut each into 8 wedges with the downward pressure of a sharp chef's knife. Serve warm or at room temperature.
• Variations
• For large tarts, prebake 2 10-inch Free-Form Tart Shells. Divide the onion mixture between them and bake the tarts until the filling is set in the center, 20 to 25 minutes. Using a large spatula, transfer them to a cutting board and cut each into 12 wedges.
• Herb Substitutions
• In place of sage, use an equal amount of finely chopped rosemary, marjoram, savory, English thyme, or lemon thyme.