By Emily Weinberger for Food Network Kitchen

If you know anything about frittatas you know they are versatile and completely customizable — they're great for using up nearly wiltly produce and the perfect vehicle for jazzing up leftovers. They are perfect for breakfast but equally as satisfying for lunch and dinner. The humble frittata can truly be a stress-free option for busy weeknight meals or when cleaning out the fridge, feeding a crowd or preparing a make-ahead meal — all you need is to follow this simple equation (no recipe required!) But have no fear, if a recipe is what you are searching for, we have lots of those for you too!

Basic Frittata Equation

12 large eggs + 1/3 cup heavy cream + 2 cups filling + 1 cup cheese

• The eggs are the foundation ingredient. Using a dozen eggs will yield a frittata that feeds 6 to 8 people.
• The cream is essential to making the frittata rich and tender. But if you don’t have cream, you can substitute milk, half-and-half or even sour cream.
• The fillings give your frittata personality. Certain fillings need to be cooked prior to being added to the eggs (onion, garlic, raw meat) while others can simply be stirred into the eggs without cooking (fresh herbs, leafy greens, deli meats).
• The cheese helps add flavor and a creaminess that will have you running back for more. Choose just one type of cheese or toss in a few different types.

How to Cook a Fritatta

Our favorite way to cook a frittata is low and slow in the oven. This is hands-down the most important element, as it results in an ultra-creamy, not-one-bit-spongy frittata. It requires a few extra minutes cooking time, but trust us, it's worth it.

Our rule of thumb is to bake the frittata in an oven-safe 10-inch nonstick skillet at 300 degrees F until the eggs are just set and no longer jiggly in the middle, 50 to 55 minutes. If you notice the edges of the frittata starting to puff up, your oven may be too hot. Open the door for a few seconds to let out a little heat and watch the frittata carefully, pulling it just as soon as it looks done. Using a nonstick skillet is key: It allows you to slide the finished frittata onto a cutting board without the risk of it breaking.

The cooking method you use will depend on your fillings:

One-step cooking method: If your fillings don't need to be cooked (see below), add them to the bowl with the eggs, cream and cheese (all whisked together), then pour the mixture into the skillet and bake as directed.

Two-step cooking method: Go this route if you are using fillings that require cooking prior to baking (see below). Simply cook the fillings in the skillet, drain off any rendered fat if necessary, then add your egg, cream and cheese mixture and stir to combine before baking.

Mix-Ins That Don't Need Pre-Cooking

Here are some of the ingredients that can be used straight from the fridge.

• Fresh herbs
• Sun-dried tomatoes
• Deli meats
• Leafy greens
• Frozen peas (thawed)
• Frozen broccoli florets (thawed)
• Smoked salmon
• Capers (rinsed and drained)
• Roasted red peppers (drained well)
• Marinated artichokes (drained well)
• Leftovers, such as roasted potatoes and leftover bacon from brunch

Mix-Ins That Do Need Pre-Cooking

Thse types of fillings should be cooked before they're added to the eggs.

• Any vegetable that may release moisture during cooking (think mushrooms, zucchini and tomatoes) should be cooked beforehand, or you run the risk of watering down your eggs. Similarly, you'll want to squeeze sauteed spinach to remove excess moisture.
• Tough vegetables like potatoes, squash and onions need to be pre-cooked since they will not have time enough to soften before the eggs are done.
• Raw meats such as bacon and sausage also need more time and heat to cook through safely, so get them prepped before your other ingredients.

Winning Frittata Combinations

If you are looking for inspiration, try these Food Network Kitchen favorites.

• Three-Cheese: Choose among Parmesan, mozzarella, fontina, ricotta, pecorino amd Cheddar.
• Spinach, Sun-dried Tomato and Goat Cheese
• Pea and Prosciutto
• Smoked Salmon and Capers
• Potato, bacon, Cheddar and chives
• Mushroom and Asparagus