Meanwhile, in a small saucepan, over low heat, melt 3 tablespoons butter, stir in flour and add milk. Stir until thick and bubbly.
In batches, pour the soup into a blender and pulse for a few seconds, then puree until smooth.
Add soup to flour mixture. Season with garlic salt and pepper and stir in cheddar cheese.
If desired, garnish with more cheese and bacon.