Grate cheeses on the large grater and set aside. Dice jalapenos and discard the seeds. Smash and mince garlic. Dice bell pepper and green onions and set everything aside. (If you want spicier dip, use older jalapenos. Use younger jalapenos for less spice.)
Melt butter in a bottom-heavy sauce pot, over medium to medium-low heat.
Add diced peppers and garlic and saute until peppers start to soften.
Sprinkle flour over the top and stir to coat the peppers with flour. Slowly pour in heavy whipping cream while whisking continuously.
Add cheeses to the pot, one handful at a time, while slowly stirring. Continue stirring with the whisk until cheese is all melted and smooth.
Stir in green onions and season with some salt and cayenne pepper (if using) and take off heat. Serve right away with your favorite tortilla chips.