Half a pan of lasagna becomes a crisp-edged, custardy frittata for two. Break up the cold pasta and layer it with eggs, then finish under the broiler. This is the fastest way to turn yesterday's dinner into something entirely new.

Serves 2. 20 minutes, 8 at the stove.

About 240 calories a serving, 17 g protein, 1 g carbohydrate, 18 g fat. From USDA figures for 67% of the ingredients; amounts are the recipe's.

1. Heat the broiler to high. Crack 6 eggs into a bowl, add a pinch of salt and pepper, and whisk until combined, about one minute.
2. Melt 1 tablespoon butter in a ten-inch nonstick skillet over medium heat. While it foams, break up the lasagna into rough chunks and scatter them across the pan, letting them warm and crisp at the edges, about two minutes.2 min
3. Pour the egg mixture evenly over the lasagna and stir gently once, so the noodles are distributed. Let it cook undisturbed until the edges set, about four minutes; the center will still jiggle.4 min
4. Slide the skillet under the broiler and broil until the top is set and lightly golden, two to three minutes. The frittata is done when the center no longer wobbles when you shake the pan gently. Slide it onto a board, cut in half, and serve right away.3 min

Note Swap the lasagna for any cooked pasta or rice and leftover meat or vegetables. Leftovers keep three days in the fridge and reheat in a dry skillet over medium heat. Serve with a green salad or hot sauce on the side.

Leftover lasagna becomes something warm and comforting in twenty minutes. Break it into pieces, soak it in an egg custard, then bake until it sets. This is how you turn half-eaten dishes into dinner.

Serves 2. 30 minutes, 10 at the stove.

About 1070 calories a serving, 42 g protein, 171 g carbohydrate, 23 g fat. From USDA figures for 83% of the ingredients; amounts are the recipe's.

1. Heat the oven to 375°F [190°C]. Butter a 2-cup baking dish.
2. Break the two portions of lasagna into rough 2-inch pieces and scatter them in the dish. Whisk 2 large eggs with 1/4 cup water, 1/4 teaspoon salt, and 1/4 teaspoon pepper until smooth. Pour this custard over the lasagna pieces and let them soak for 2 minutes, stirring gently to make sure the liquid settles between the layers.
3. Tear 2 oz cheese into small pieces and scatter over the top. Slide the dish into the oven.
4. Bake until the custard is set but still soft in the center and the top is golden, about 18 to 20 minutes. A knife inserted off-center should come out clean. Let it rest for 2 minutes before serving.20 min

Note Swap the cheese for any sharp white cheddar or provolone. Leftovers keep covered for two days and reheat gently in the oven. Serve with a green salad and crusty bread to soak up any extra custard.

A lasagna half-layer turns into a savory frittata that feeds two tired adults on a weeknight. The pasta and sauce cook down into the eggs, and you're done in one skillet before ten o'clock. This is the kind of dinner that turns yesterday's big project into tonight's simple meal.

Serves 2. 20 minutes, 15 at the stove.

About 470 calories a serving, 23 g protein, 38 g carbohydrate, 25 g fat. From USDA figures for 100% of the ingredients; amounts are the recipe's.

1. Heat 2 tablespoons of butter in a 10-inch skillet over medium heat. Break the lasagna half-layer into rough 2-inch pieces and scatter them across the pan, then let them warm through for about two minutes while you crack 6 eggs into a bowl.2 min
2. Whisk the 6 eggs with a pinch of salt and pepper until they are pale and just combined. Pour the eggs over the lasagna pieces and stir gently to distribute the pasta and sauce throughout.
3. Let the eggs cook without stirring for five minutes, until the edges begin to set and pull away from the sides of the skillet, while the center still jiggles when you nudge the pan.5 min
4. Tilt the skillet toward a burner edge or transfer to a 400°F [200°C] oven for three minutes, until the top is just set but still glossy. The frittata is done when a fork run through the center meets almost no resistance.3 min

Note To soak up the eggs, serve with a simple green salad dressed with oil and vinegar. Leftovers keep for two days covered in the cold fridge and taste best eaten cold or warmed gently in a low oven.