Cook pasta according to package directions; drain and set aside.
In medium sauté pan, melt 2 tablespoons butter and add onions and pinch salt. Cook until onions are translucent; about 5 minutes. Add corn, poblanos and jalapeños; cook 3-5 minutes. Season with salt and pepper; set aside.
In medium saucepan, melt 2 tablespoons butter over medium heat. Whisk in flour until roux forms; cook 2 minutes until bubbling and reduce heat to low. Cook 2-3 minutes more. Whisk in heavy cream and increase heat to medium, allowing cream to thicken.
Slowly whisk in cheese until it is completely melted. Add garlic salt and salt and pepper to taste.
In large bowl, add cooked pasta, corn and pepper mixture, and cheese sauce. Gently toss to coat. Garnish with cilantro and serve immediately.
Frozen corn can be substituted.