Heat the oil in a large pot over medium heat.Add garlic and saute for just a quick second.Add the flour while using a whisk.Cook for about a minute. It will be a big clump.Add the chicken stock and stir until the clumps thin out.Whisk in the milk and let simmer for about a minute.Stir in your cheese and salt and pepper.Reduce heat and let simmer for another 5 minutes.Remove from heat and leave on stove top until ready to assemble your recipes. The longer it cooks, the thicker the sauce gets.