Bring a large pot of salted water to a boil and cook the pasta according to package instructions until al dente.
Drain and set aside.
Step 2: Prepare the Green Chile Mixture
In a skillet over medium heat, add the olive oil and sauté the chopped onion until it’s soft and translucent, about 5 minutes.
Add the garlic and cumin (if using) and cook for another minute, until fragrant.
Stir in the diced green chiles and cook for another 2-3 minutes, allowing the flavors to meld.
Remove from heat and set aside.
Step 3: Make the Cheese Sauce
In a medium saucepan, melt the butter over medium heat. Sprinkle in the flour, whisking constantly, to form a roux (this should resemble a thick paste).
Gradually pour in the milk, whisking continuously to avoid lumps. Let it cook for about 5-7 minutes until the sauce thickens.
Stir in the heavy cream, if using, for an extra creamy texture.
Add the shredded cheese, a little at a time, whisking until the cheese is melted and the sauce is smooth.