Queso

Take 8 oz of your favorite (Mexican) cheese, toss with corn starch, melt with a can of evaporated milk. Bam, instant cheese sauce. You can add peppers, hot sauce, Worcestershire sauce, whatever. The trick is that the evaporated milk and corn starch keep the grease from separating from the cheese. The fattier/greasier the cheese, the more you need (so if you're using something like cheddar, use less). This describes the science behind it for American nacho cheese, but the principle is the same: http://aht.seriouseats.com/archives/2010/09/the-burger-lab-cheese-sauce-for-burgers-fries-and-chips.html