Heat oven to 375°F. In large bowl, mix peanut butter and milk until smooth. Stir in Bisquick mix and vanilla until blended. 2 Shape dough into 1 1/4-inch balls. Roll tops in sugar. On ungreased cookie sheet, place balls, sugar sides up, 2 inches apart. Flatten in crisscross pattern with fork dipped in additional sugar. 3 Bake 7 to 9 minutes or until centers are set and bottoms are light golden brown. Do not overbake. Remove from cookie sheet to cooling rack. Cool 15 minutes.