Pre-heat the oven to 350°F. Bring a pot of water to a boil for the pasta.
Heat a large skillet with the olive oil, two turns of the pan, over medium to medium-high heat. Add the vegetables and scapes or garlic and season with salt and pepper. Sauté to tender-crisp, 5 minutes or so. Turn off the heat; douse with the lemon juice and add the tarragon.
In a medium size high-sided skillet or pot, melt the butter over medium heat. Add the flour and whisk for 1 minute; whisk in the chicken stock and thicken for 1-2 minutes. Slowly whisk in the warm milk and season the sauce with salt, pepper and nutmeg, to taste. Thicken to lightly coat the back of a spoon. Stir in the Fontina or Gruyère and Asiago in a figure-eight motion, a handful at a time, using a wooden spoon.
Undercook the pasta by 2-3 minutes in salted boiling water, 6-7 minutes, according to the package directions. Drain the pasta and add back to the pot with the cheese sauce and vegetables. Stir to combine, then adjust the salt and pepper, to taste. Transfer to a casserole and cover with the Parm. Bake to brown and bubbly, 20-25 minutes.
This is one of many “Yum-o!” recipes – it’s good and good for you. To find out more about Yum-o!, Rachael’s nonprofit organization, visit