Preheat oven to 400°F, prepare pans. In a small saucepan (or microwave) heat chocolate chips & butter until melted, stirring constantly; remove from heat & reserve. In a bowl stir together flour, sugar, b/pdr & salt. In another bowl stir together milk, p/butter, oil, egg & vanilla. Add dry mix to wet mix until just combined. Spoon half of batter into pans. Divide chocolate mixture among muffins, a scant teaspoon per pan; do not let filling touch sides of pan. Spoon remaining batter over filling. Sprinkle tops of muffins with chopped peanuts if desired. Bake for 20-25 mins or until lightly browned. Makes 9 muffins. Variation: A ripe banana cut into 1/2" thick slices & dipped in orange juice may be used instead of the fudge filling.