Preheat The Oven To 350 Degrees.
Heat butter in a large skillet over medium temperature. Add the squash, jalapeno and onion, and sauté to allow onions to become translucent and the squash is tender for almost ten minutes.
Add the garlic, chili powder, cumin, cayenne, pepper, salt, and allow it to cook for a few more seconds. Then add flour and cook until a light-brown past is formed which takes a minute.
Now add the tomatoes and broth and stir occasionally until the mixture concentrates, which should appear in a couple of minutes. Add the half and half, cilantro and sour cream and remove it from the heat.
In a greased casserole dish, make a layer in the bottom with the crushed tortilla chips. Spread on top of the chips the creamy squash mixture and then scatter the whole dish with the grated cheese.
Cook without covering for thirty minutes, or until top is brown and bubbling.