Step 1

Set your oven rack about 4 inches from the broiler and turn on the broiler. Place the peppers on a foil-lined baking sheet and broil until the skins char and blister, about five minutes. Using tongs, rotate the peppers a quarter turn and continue broiling until all the sides are blistered and blackened.

Step 2

Immediately transfer the peppers to a bowl and cover the bowl tightly with storage wrap. Let the bowl stand covered until the peppers are cool enough to handle, at least 20 minutes. Editor's Tip: A resealable plastic bag would also work in place of the covered bowl. Trapping the peppers with steam will make them "sweat," making the skins easier to peel later.

Step 3

Cook the spaghetti according to the package directions until al dente.

Step 4

Peel the charred skin from the peppers and discard the skin. Split the peppers open and pull out the ribs and seeds; discard the ribs and seeds. Roughly chop the peppers and add the pieces to a blender. Add the cream cheese, onion, sour cream, stock, cilantro, garlic, salt and pepper. Cover and blend until smooth.

Step 5

Melt the butter in a large skillet over medium heat and add the sauce. Cook until warmed through, stirring occasionally, about three minutes. Add the drained pasta to the skillet and stir to coat in the sauce. Serve sprinkled with Cotija cheese and cilantro.