12 large eggs
1⅓ cups ricotta cheese, fresh or whole milk
¼ cup heavy cream
freshly ground black pepper
1⅓ cups day old bread, cubed (1/12-inch), crusts removed
3 tablespoons extra-virgin olive oil
1 onion, cut into 1/2-inch strips
1 red bell pepper, cores, seeded, and cut into 1/4-inch slices
1 green bell pepper, cored, seeded, and cut into 1/4-inch slices
1 tablespoon unsalted butter
Preheat the oven to 350 degrees F. Beat the eggs, heavy cream, and salt and pepper to taste in a large bowl. Add the bread cubes and let soak until softened, about 15 minutes.
Heat 2 tablespoons of the olive oil in a 10-inch cast iron or non-stick skillet with a heatproof handle over medium heat. Add the onion and cook until wilted, about 4 minutes. Add the peppers and cook, stirring until crisp-tender, about 5 minutes. Season well with salt and pepper. Add the butter and the remaining 1 tablespoon oil to the skillet and heat until the butter is foaming. Add the egg mixture to the pan and cook, still over medium heat, without stirring, just until the bottom is lightly browned, about 5 minutes. Drop 1 1/3 cups fresh or whole-milk ricotta into the egg by the rounded tablespoonful, forming little pockets of ricotta throughout the frittata. There should be a few bubbles at a time around the edges-any more than that means the frittata is cooking too quickly and the bottom will be too brown. In that case, remove the skillet from the heat, reduce the heat, and let the skillet sit a minute or two before returning it to the heat.
Transfer the skillet to the oven and cook just until the center is set -firm to the touch - about 25 minutes. If the edges are set and beginning to brown before the center is set, remove the frittata from the oven and finish the frittata under the preheated broiler.
If you'd like to serve the frittata hot, let it stand at room temperature at 15 minutes. If you prefer it warm or at room temperature, let it stand a little longer. Run a rubber spatula around the edges of the frittata and shake the pan gently to free the bottom of the frittata. You can serve the frittata right out of the pan or slide it out onto a serving platter.