Easiest Baked Mac & Cheese

Ingredients

• 2 tablespoons butter, cut into cubes
• 1 cup sour cream (or ricotta, crème fraiche, or mascarpone)
• 2 cups milk
• 1 teaspoon dry mustard
• Pinch cayenne
• 1/2 teaspoon fine sea salt
• 1/4 teaspoon black pepper
• 1 pound extra sharp cheddar (I used an 8 ounce block of both yellow and white)
• 1/2 pound uncooked elbow pasta