• 2 TBS extra-virgin olive oil
• 2 TBS unsalted butter
• 1 cup yellow onion, chopped
• 2 garlic cloves, chopped
• 5 (9 oz.) bags fresh spinach
• 1/2 cup all purpose flour
• 1 cup heavy whipping cream
• 2 tsp. salt
• 2 cups shredded mozzarella cheese, divided
• 1 cup grated Parmesan cheese, divided
• 1/2 cup shredded Asiago cheese

Preheat oven to 400 degrees. Spray a 2-quart baking dish with non-stick cooking spray.

In a large non-stick skillet, combine olive oil and butter. Cook over medium heat until butter melts. Add onion and garlic. Cook until onion begins to be translucent, 4 to 5 minutes.

Raise heat to medium-high. Working in batches, add spinach to pan. Cook, stirring often, until spinach wilts, 3 to 4 minutes per batch. Repeat process with remaining spinach until all spinach is wilted, stirring often. To reduce liquid, cook for an additional 3 to 4 minutes, stirring often.

Sift flour over spinach, stirring to combine. Cook until thickened, 2 to 3 minutes. Add cream and salt, stirring well. Cook until thickened, 2 to 3 minutes and remove from heat.

Add 1 1/2 cups of shredded mozzarella, 1 cup of Parmesan and 1/2 cup Asiago, stirring well. Spoon into prepared dish.

Cover and bake in preheated 400 degree oven for 15 minutes. Remove cover and spread remaining 1/2 cup mozzarella over top. Bake until cheese is golden brown, about 10 minutes.