1 Lb. Gnocchi (I used pre-packaged)
6 Slices Bacon
1 Sweet Onion, chopped
2 Tbsp. Butter
2 Cloves Garlic, finely chopped
8 Sage Leaves, finely chopped (I used a small palm full of dried)
1 Tbsp. Flour
1 Cup Milk
1 Tbsp. Ground Mustard (omitted-I didn't have any)
1/2 Cup (or more) Gruyere Cheese, shredded
1/2 Cup (or more) Fontina Cheese, shredded
1/2 Cup (or more) Parmigiano-Reggiano Cheese, shredded
Preheat oven to 375.
Cook bacon in a large skillet over medium low heat, turning frequently until crisp. Transfer bacon to a paper towel lined plate, chop and set aside. Add onion to the skillet with the bacon grease and cook, stirring occasionally, until golden and caramelized, anywhere from 10-30 minutes.
Drop the gnocchi into a pot of salted boiling water and cook until they float to the top, 2-3 minutes. Drain in a colander then return gnocchi to the pot.
Melt the butter in a saucepan over medium heat. Stir in the garlic and sage and cook until fragrant, about 30 seconds. Add the flour and whisk until it bubbles, then add the milk and ground mustard. Cook until slightly thickened, about 3-5 minutes.
Add the Gruyere and Fontina and stir until melted. Mix in the bacon and caramelized onions. Pour over the gnocchi and stir until combined.
Transfer the gnocchi and sauce to a lightly oiled baking dish and cover with the Parmesan cheese. Bake until the cheese is golden and bubbly, about 25 minutes.
Let stand 5 minutes before serving.