Melt butter in a small saucepan over medium-low heat. Add flour and whisk for about 30 seconds until completely combined.
Add jalapeño and garlic, whisk another 30 seconds.
Stir in 1/4 cup milk slowly until the sauce starts to thicken. Slowly add the remaining 1/4 cup of milk in the same way.
Stir 1-2 minutes until the sauce becomes thicker.
Pour in the beer in the same manner you added the milk, whisking slowly to combine.
Bring to a quick boil, then turn back down to low heat.
Add mustard, seasoned salt and pepper, and let the sauce set for 4-5 minutes, stirring occasionally.
Grate in the cheese and add the paprika and cayenne, whisking slowly to combine. Feel free to let this set for another few minutes, stirring occasionally.
Serve hot!
Notes
Add more garlic or jalapeño if you like. You could also substitute minced garlic for garlic powder!