In her book In My Kitchen, Deborah Madison shares some of her best secrets for brightening up ordinary vegetables, like this frittata that’s finished with a rich, sharp sherry vinegar sauce.
Frittatas with caramelized onions have long been a favorite of mine. What makes them special is the wash of melted butter and vinegar sauce spooned over the finished dish. It’s made in the pan in just a few seconds. You can serve it whole or cut it into squares, pile it on crackers or bread, and serve as an appetizer.
- Peel the onions and halve them lengthwise, then cut each half into thirds or quarters. Slice each piece crosswise about 1/4 inch thick.
- Warm the olive oil in a medium-sized skillet, add the onions, and cook over medium heat, stirring occasionally until they begin to color. Reduce the heat to medium-low, cover the pan, and continue to cook, stirring occasionally, until they've started to color, about 20 minutes. Remove the lid and stir frequently, keeping an active eye on them to make sure they don't burn.
- When they're limp and caramel colored, raise the heat, add the vinegar, and let it reduce. Season with salt, pepper, and the cloves. Taste, and if you want a little more vinegar, add it—carefully. Sherry vinegar is strong. You can use the onions right away or refrigerate for several days.
- Whisk the eggs with a few pinches of salt and some freshly ground pepper, then stir in the parsley and the caramelized onions. Heat your broiler.
- Melt 2 teaspoons of the butter in a 10-inch skillet until it’s sizzling, then add the eggs and lower the heat. Cook the eggs, covered, until they are set and golden on the bottom, about 6 minutes for a thin frittata, longer for a thick one.
- Grate a little of the cheese over the top, then slide the pan under the broiler to finish cooking. The top should be light gold and firm. Loosen the frittata and tilt it onto a plate, then return the pan to the stove and raise the heat.
- Add the remaining butter to the pan, and when it begins to foam, add the sherry vinegar. Slide the pan back and forth to emulsify the two. Stand back! The vinegar fumes are strong. When you have a sauce, pour it over the frittata and serve.