Combine butter and flour in a saucepan over medium-low heat and make a blonde roux. Add milk and cream, combine thoroughly with wire whisk and bring to a boil. Transfer mixture to a double boiler and add both cubed cheeses. Stir frequently, and once cheese melts into sauce, add all other ingredients and combine thoroughly.

Transfer queso to serving dish and pour a scant 1/4 oz. of 151 or tequila over the top. Light carefully with a match. Serve with corn tortilla chips or warm flour tortillas for dipping. Dip can also be served with skewers of steak and chicken.