This substantial frittata is best served room temperature and makes for excellent leftovers. Makes ~6 servings.

1 bunch Red Dog raab
¾ pound hot Italian sausage, loose or in links
2 tablespoons extra-virgin olive oil
1 medium onion, diced
Salt and black pepper
3 cloves garlic, minced
2 teaspoons roughly chopped rosemary
1 ½ cups ricotta
3 ounces grated provolone (about 1 1/4 cup)
3 ounces grated Parmesan (about 3/4 cup)
4 ounces grated smoked mozzarella (about 1 1/2 cup)
10 eggs, lightly beaten and seasoned with salt and pepper

Heat oven to 350 degrees. Bring a large pot of salted water to boil. Add raab and cook for 1 minute, just to wilt, then remove, rinse with cold water and drain. Roughly chop greens, then squeeze to remove excess water and set aside.

Heat a 10-inch cast-iron skillet over medium-high heat. Add sausage (remove casings from links first) and cook, stirring and mashing, until sausage is in large, well-browned crumbled pieces, 6 to 8 minutes. Remove cooked sausage, blot on paper towels, and set aside.

Add olive oil to skillet. When oil is hot, add onion and cook, stirring, until softened and lightly browned, about 5 minutes. Season well with salt and pepper, then add garlic and rosemary and cook for 1 minute more. Turn off heat and stir in chopped greens and reserved sausage. Let mixture cool in pan.

Spoon dabs of ricotta over greens mixture, then sprinkle evenly with provolone, Parmesan and mozzarella. Pour seasoned eggs over, tilting pan to distribute.

Bake for 30 to 35 minutes, until top is golden and eggs are no longer runny at the center. (Use a skewer or paring knife to check; residual heat will continue to cook frittata as it cools.) Let cool at least 15 minutes, then cut into wedges.