In a medium saucepan, melt the butter over a medium-high heat. Add the flour and watch it until the mixture turns creamy looking, and then begins to look a little grainy, about 5-8 minutes. Be sure the mixture doesn't turn too dark. You're looking for a "blonde" roux. Add the milk and continually whisk until sauce has reached the desired thickness. Add salt and pepper to taste.

Add cheese and mix thoroughly.

Once the sauce has reached desired thickness, serve over tortilla chips and garnish with parsley.