i have a slightly different florentine sauce that i make with eggs occasionally. it makes a bed of sauced spinach upon which you place the eggs, but if you reduce the spinach a bit, i think it'll work with a baked pasta dish.
2 (10-oz) boxes frozen chopped spinach
1 medium onion, chopped
2 tablespoons olive oil
1 1/4 cups half-and-half
1 teaspoon chopped fresh thyme
1/8 teaspoon freshly grated nutmeg
3/4 teaspoon salt
1/2 teaspoon coarsely ground black pepper
cook onion in oil in a 12-inch heavy skillet over moderately high heat, stirring occasionally, until softened and browned, about 8 minutes. Add half-and-half, thyme, and nutmeg and briskly simmer, stirring occasionally, until liquid is reduced by one third and slightly thickened, 2 to 3 minutes. Add spinach, salt, and pepper and simmer, stirring occasionally, until spinach is heated through, about 2 minutes.