Preheat oven to 400°F.
In large pot of salted, boiling water, dump pasta and undercook by 2 minutes. Drain and reserve.
Pulse-grind the ingredients for the pesto sauce in a food processor or hand grind them in a large mortar and pestle.
Melt butter in a saucepot over medium heat. Whisk in flour, cook 1 minute, then whisk in milk. Season sauce with salt, pepper and a little freshly grated nutmeg, simmer at a low bubble and thicken to coat the back of a spoon. Adjust seasoning to taste. Stir in Fontina and melt, reserving a handful to top casserole.
Combine pesto, white sauce and pasta in a large mixing bowl. Adjust seasonings and place in a casserole dish, top with remaining Fontina and Parm, and bake 30-40 minutes until brown and bubbly on top.