Melt 6 Tablespoons of the butter in a medium saucepan over medium heat. Add half the onions,half the bell peppers, and half the garlic and cook, stirring often with a wooden spoon, until soft, 8 to 10 minutes. Add flour and cook, stirring constantly, for 2 minutes. Stir in 2 cups of the milk and simmer, stirring often, until thick, 6 to 8 minutes. Add one teaspoon of the seasoned salt, and 4 dashes of the Tabasco sauce. Keep sauce warm over low heat.