BEAT brown sugar, peanut butter, 1/2 cup shortening, milk and vanilla in bowl of electric mixer at medium speed until well blended. Beat in egg. Combine flour, baking soda and salt in a medium bowl. Add to shortening mixture. Beat at low speed just until blended. Refrigerate about 1 hour or until firm.
HEAT oven to 350 degrees F. Spray mini-muffin pans with no-stick cooking spray.
SHAPE dough into 1-inch balls. Roll in sugar. Place each ball in prepared mini-muffin cups. Press dough onto bottom and sides of cup to within 1/2-inch of top.
BAKE 7 to 8 minutes or until cookies are set and just beginning to brown. Cool 10 minutes on cooling racks. Remove cookie cups very carefully to cooling racks to cool completely.
PLACE chocolate chips and 1 teaspoon shortening in microwave-safe bowl. Microwave at MEDIUM for 1 to 2 minutes or until chips are shiny and soft. Stir until smooth. Spoon about 1/2 teaspoon chocolate mixture into center of each cookie. Sprinkle with chopped peanuts. Cool completely.