What to do on a busy weeknight when you poke your head into the fridge and discover a variety of souvenirs left over from previous meals — including veggies, protein and starch? Just reach for a carton of eggs and turn the whole thing into a one-skillet meal. Leftovers? Not at all. The Flexible Frittata is a thick, satisfying omelet.

And just as with a French omelet, you can toss almost anything into a frittata. There are only a few rules. The first is to make sure that every ingredient has already been cooked — a frittata spends so little time in the oven that an uncooked piece of meat or a raw vegetable will never be cooked through. Secondly, all the ingredients must be chopped up before they’re added to the frittata so that they can be evenly distributed.

Otherwise, have fun. I’ve specified red bell pepper in this recipe, but you’re welcome to swap in broccoli, green beans, cauliflower, carrots, or mushrooms. Instead of sausage, you can roll with leftover pork chops, steak, rotisserie chicken or shrimp. No cartons of cooked rice sitting in the refrigerator? How about potatoes, pasta, quinoa or farro? Similarly, if you happen to be rich in scraps of various flavorful cheeses, use them to replace the Parmigiano-Reggiano.

And, happily, because most of its parts have been cooked ahead of time, making the frittata takes very little time and effort — about 40 minutes from start to finish, only 20 minutes of which is hands-on. Serve with a simple salad and some crusty bread.

Ultimately, you might decide to add a frittata like this to your weekly line-up. It’s the perfect vehicle for leftovers … but nobody digging into it will be thinking of leftovers.

The Flexible Frittata

Start to finish: 40 minutes (20 minutes active)

Servings: 6 to 8

3 tablespoons extra-virgin olive oil

1 1/2 cups chopped onion

1 1/2 cups chopped red bell pepper

2 cups chopped (halved lengthwise and sliced crosswise 1/4-inch thick), cooked Italian sausages

Dozen large eggs

1/2 cup sour cream

1 1/2 cups cooked rice

1 1/2 ounces grated Parmigiano-Regianno

1/2 teaspoon kosher salt

1/2 teaspoon freshly ground black pepper

Preheat oven to 350 F.

In a large nonstick skillet, heat the oil over medium-high heat. Add the onion and red bell pepper, reduce the heat to medium-low and cook, stirring occasionally, until softened, about 5 minutes. Add the sausage and cook, stirring occasionally, until the pieces are lightly browned, about 5 minutes.

Meanwhile, in a medium bowl, whisk together the eggs and the sour cream. Add the rice, cheese, salt and pepper; stir well. When the sausages are browned, pour the egg mixture over the meat, shaking the pan to make sure it is evenly distributed. Cook the frittata until it is just beginning to stick and set up at the edges, 5 to 8 minutes. Transfer to the oven and bake on the middle shelf until just set, 10 to 15 minutes. Remove from the oven, preheat the broiler and return the frittata to the middle shelf to brown briefly before serving.

Nutrition information per serving: 370 calories; 227 calories from fat; 25 g fat (9 g saturated; 0 g trans fats); 462 mg cholesterol; 697 mg sodium; 14 g carbohydrate; 1 g fiber; 3 g sugar; 20 g protein.

Sara Moulton is host of public television’s “Sara’s Weeknight Meals.” She was executive chef at Gourmet magazine for nearly 25 years and spent a decade hosting several Food Network shows, including “Cooking Live.” Her latest cookbook is “HomeCooking 101.”