Mix Flour, Sea Salt and Garlic Powder together in a small bowl, set aside
In a medium saucepan over medium heat, melt the Butter.
Add Flour mixture and whisk to combine
Cook for 1 minute until mixture is slightly brown
Add 1 Cup Milk and whisk until the mixture is smooth
Add Sour Cream and whisk until smooth
Cook on medium-high heat until the mixture is thickened (about 3-5 minutes) Do NOT let it boil.
Once mixture is thick (sticks to back of spatula), reduce heat to low and add cheese. Whisk until cheese is melted and mixture is smooth. Taste and add more salt/seasoning if desired.
Add cooked pasta to the pot of cheese sauce and stir until the sauce is evenly distributed.
Let the Mac and Cheese cool for 3-5 minutes or until the cheese sauce has thickened a little bit and sticks to the noodles.
Serve Warm!