heat oven to 375°F

remove wrappers from candy. line small muffin cups (1-3\4 inches in diameter) with paper bake cups.

beat butter, sugar, brown sugar, peanut butter, egg and vanilla until fluffy in large bowl. stir together flour, baking soda, and salt; gradually add to butter mixture, beating until well blended. shape dough into 1 inch balls; place one in each paper-lined or ungreased muffin cup. Do not flatten.

bake 10 - 12 minutes until puffed and lightly browned; remove from oven. immediately press peanut butter cup in center of each cookie. cool completely in muffin pan.