In a medium sauce pan, melt 2 tbsp unsalted butter over medium heat. Once melted, add garlic and cook about 1 minute. Then add flour and whisk constantly and cook about 1 more minute.
Then add the flour and cook again for another minute, whisking frequently. We let the flour cook like this for a minute to get rid of the raw flour taste.
Slowly pour in milk, whisking constantly. Increase heat a touch and whisk occasionally while allowing to cook until gently simmering and bubbling around the edges of the pan.