Preheat oven to 375 degrees F. Lightly spritz a 9×13 dish with nonstick spray.

Heat a large skillet over medium heat and add olive oil. Add onions, garlic and sage, cooking for 2-3 minutes until slightly softened. Toss in squash, salt, pepper and 1/4 teaspoon nutmeg, stirring well to coat. Cover and cook for 8-10 minutes. You don’t want to overcook the squash because it will be mushy, so cook until it’s slightly tough but you can bite through a few pieces. Make sure to taste 2-3 pieces! Once finished, stir in beans and mix well. Remove squash and bean mixture, placing in a large bowl and drizzle with brown butter, then toss with 1/2 cup fontina. Set aside.

In the small skillet, raise the heat to medium-high and add butter. Once sizzling add in the flour and whisk for 2-3 minutes until a golden, nutty roux forms. Pour in stock and milk, whisking again until bubbly and slightly thick. Reduce heat to low and stir in 1 cup of fontina, stirring until combined. Add in remaining nutmeg and taste to season with additional salt and pepper if desired. Spoon about 1/3 cup of sauce into the bottom of the baking dish, then spoon a few spoonfuls of the squash mixture in the center of each tortilla, rolling up tightly. Place all the rolled tortillas carefully into the dish, then cover with remaining sauce. Sprinkle with the rest of the cheese and some extra chopped sage. Bake for 20-25 minutes, until cheese is bubbly and melted. Serve immediately!