Add chorizo to a large skillet and cook over medium high heat. Break up sausage with the back of a wooden spoon. Continue cooking until chorizo has started to brown and add the mushrooms.
Cook the chorizo mushroom mixture for another five minutes and then add the tomato sauce and paste.
Mushrooms have a ton of water so the mixture will become quite wet. Reduce the heat to low, and simmer for about 20-25 minutes until most of the water has evaporated and the sauce is quite dry.
White cheddar cheese sauce:
Melt butter in a medium sized skillet over medium heat and whisk in the flour. You want to cook this for about two minutes, whisking constantly.
Slowly add the milk and continue to whisk. The sauce should thicken in about five minutes.
Once thickened, add the grated cheese and stir until melted and smooth.
Bake the fries according to the package, but remove them from the oven ten minutes before they are done.
Pre-heat the oven to 400°
Using an 8”x10” inch pan, spread about 1/2 cup of the chorizo tomato sauce all over the bottom of the pan. Line the sauce covered bottom of the pan with a layer of the fries. Cover the fries with some more of the chorizo tomato sauce and lay four of the crispy prosciutto pieces over the sauce. Top this with some of the mozzarella rounds and dot with some of the pesto and caramelized onions. Cover with cheddar sauce. Repeat this twice.
Put the Frasagna in the oven for 15 minutes. Turn the oven to broil and broil Frasagna for five minutes, or until the top is bubbly and golden brown.