INGREDIENTS
Unsalted butter, softened, for brushing
1 lb
spaghetti
3
tablespoons extra-virgin olive oil
1
medium yellow onion, minced
2
garlic cloves, minced
1 lb
mixed wild mushrooms, such as cremini, porcini and stemmed shiitakes, cut into 1-inch pieces
Kosher salt
Pepper
5 oz
baby spinach
3
large eggs
1 1/2 cups
whole milk
3 cups
shredded Fontina cheese (10 ounces)
1 cup
fresh ricotta cheese
1 cup
finely grated Parmigiano-Reggiano cheese
1 tbsp
finely chopped sage
1 tbsp
thyme leaves