In a mixing bowl, cream butter, peanut buffer and sugars; add egg and vanilla. Stir together flour, baking soda and salt; add to creamed mixture. Mix well. Chill for 1 hour. Shape into 48 balls, 1 in. Each. Place in lightly greased mini-muffin tins. Bake at 325 for 14-16 minutes or until lightly browned. Remove from oven and immediately make "wells" in the center of each by lightly pressing with a melon baller. Cool in pans for 5 minutes, then carefully remove to wire racks. For filling, melt chocolate chips in a double boiler over simmering water. Stir in milk and vanilla; mix well. Using a small pitcher or pastry bag, fill each shell with filling. Sprinkle with peanuts. (Leftover filling can be stored in the refrigerator and served warm over ice cream.) Yield: 4 dozen.