Heat the oil in a large skillet over medium heat and brown the mushrooms, 10 minutes. Scrape the corn
kernels from the cobs and add to the mushrooms. Season with salt and black pepper and continue cooking, 5 to 6 minutes.
Puree the stock with the poblanos, garlic, cilantro
and some salt and black pepper in a blender
or food processor
the butter in a saucepot over medium heat, and then whisk
in the flour. Whisk in the milk and cream and raise the heat a bit. Stir in the poblano puree and simmer
until thickened, 20 to 25 minutes. Stir in 1 cup of the grated cheese.
Preheat the oven to 350 degrees F.
Cook the pasta to al dente
in a large pot of salted boiling water. Before draining the pasta, reserve a ladle of the starchy cooking water. Toss the pasta
with the sauce, mushrooms
and corn, adding a little of the reserved starchy water if the sauce
is too thick. Pour into a baking dish
and top with the remaining cheese. Bake until brown and bubbly, 15 to 20 minutes.
Cook's Note: For a make-ahead meal, cool and store before baking. Let the mac n cheese come to room temperature before baking 30 to 40 minutes.