In a large mixing bowl, beat the brown sugar and peanut butter until smooth. Add the egg. Beat just until mixed into batter, about one minute. Stir in the milk chocolate chips and raisins.
Line cookie sheets with parchment paper. Using a melon baller, or a teaspoon, scoop batter into 2-inch balls, and place four inches apart on cookie sheet. Flatten each ball with a fork into a criss-cross pattern. Sprinkle sugar on top of each cookie. Bake 8 minutes. Cool cookies on tray for 5 minutes, then slide parchment sheet off tray. Carefully remove cookies from sheet with a spatula. Cool on rack.