Scrub potatoes with a brush; pat dry, and prick with fork. Bake in a 425 degree F oven for 40 to 60 minutes or until tender. Cut a lengthwise slice from the top of each potato; discard skin from slice and place pulp in bowl. Scoop pulp out of each potato, leaving a 1/4-inch-thick shell. Add pulp to bowl.
Mash potatoeswith a potato masher or an electric mixer on low speed. Add sour cream, garlic salt, and pepper; beat until smooth. If necessary, stir in 1 to 2 tablespoons milk to make of desired consistency.
Spoon the potato mixture into the shells. Place in a 2-quart sqaure or rectangular baking dish. Bake, uncovered, in a 425 degree F oven for 20 to 25 minutes or until lightly browned. Sprinkle with Gorgonzola or blue cheese and chopped red sweet pepper. Makes 4 servings.