Preheat oven to 350° F. Cut the squash in half length-wise and scoop out the seeds. Rub with olive oil, season with salt and pepper and place cut side down in a heavy baking dish with a clove or two of garlic in each seed cavity. Bake covered for 45 minutes, or until the flesh is tender. Remove and cool.
Boil pasta as per directions in plenty of salted water, strain when al dente and shock under cold water.
Score the flesh side of the squash into 1 inch squares and scoop out the diced flesh with a spoon.
Prepare the sauce by making the white roux. Melt 3 ounces of unsalted butter over moderate heat and add the diced onion. Gently simmer for 2 minutes and add the chopped garlic, simmer for 1 more minute. Slowly whisk in the flour and stir until smooth. Cook, stirring constantly for one minute, remove from heat and reserve.
Scald the milk, do not boil, and pour it over the roux. Bring to a boil stirring attentively as to not burn. Bring down to a gentle simmer and slowly add the cheese. Add the wine and adjust the salt and pepper.
In a large bowl toss the pasta, squash, pecans, sage and as much sauce as you feel comfortable with. Pour into a buttered deep casserole dish top with more cheese and bake covered for 20 minutes. Uncover and bake for 10 minutes more. Garnish with sage.
This dish work very well with Gorgonzola, prosciutto and walnuts as well.Makes 4 to 6