Cook ground beef in a skillet over medium heat, breaking it up until fully browned

Add diced onion and cook until softened, about 3–4 minutes

Stir in garlic, chili powder, cumin, smoked paprika, salt, and pepper; cook until fragrant

Remove chili mixture from heat and set aside

Melt butter in a saucepan over medium-low heat

Whisk in flour and cook briefly until smooth, keeping it pale

Slowly whisk in milk, stirring constantly until slightly thickened

Reduce heat to low and add cheeses gradually, stirring until fully melted and smooth

Stir in cooked chili mixture until evenly combined

Add jalapeño juice and diced jalapeños if using

Taste and adjust seasoning or spice level

Serve warm or keep on “warm” setting in a slow cooker