In a large bowl, combine the shortening and peanut butter. Mix well. Add ⅓ cup sugar and the brown sugar. Beat in the egg, milk, and vanilla extract.
In a small bowl, combine the flour, baking soda, and salt. Gradually mix the dry ingredients into the peanut butter mixture.
Shape the dough into 1-inch balls, roll in sugar, and place on a cookie sheet lined with parchment paper.
Bake at 375 degrees for 7-8 minutes.
Remove wrappers from Hershey's Chocolates.
Immediately press a Hershey's chocolate into the center of each cookie after the cookies come out of the oven. The cookies will crack around the edges. Cool cookies completely on a wire rack.
Place green frosting in a ziploc bag and barely cut off a corner of the bag. Decorate cookies with frosting and sprinkle with holiday sprinkles.
Recipe by Saving Cent by Cent at https://savingcentbycent.com/2014/11/28/christmas-tree-peanut-butter-blossoms/