In a large skillet set over medium heat add the butter. When the butter has melted, add the onion, garlic and jalapeño. Saute for 3-4 minutes or until soft and fragrant.
Add the chopped chilies, then the half & half. Whisk in the cornstarch and bring to a low simmer. Turn the heat to low, whisk in the mustard, paprika, coriander and black pepper.
When the mixture is smooth, sprinkle in the cheese a little at a time and continue to whisk until smooth and creamy. Serve immediately.