Preheat oven to 375 F. In a large bowl, cream together the butter and brown sugar. Beat in the peanut butter, egg and vanilla. Stir in the flour, salt and baking soda. Roll into 36, approximately 1-inch balls. Roll each ball in granulated sugar.
Bake at 375 F for 8-10 minutes or until lightly browned around the edges. Remove from the oven and immediately press an unwrapped Hershey Kiss into the center of each cookie. If making reindeer cookies, press the broken pretzel pieces into the cookies for antlers as well. Let cool on cookie sheet for 2 minutes before removing to a wire rack to cool completely.
Let cookies cool completely and until Hershey kisses are no longer melted. Then decorate.
To make the reindeer cookies, add two little eyes with the black writing gel. And pipe a dot of red frosting on the top of the Hershey kiss for a nose.
To make the Christmas trees, pipe green frosting in a spiral around the Hershey kiss. Then, add add the sprinkles for ornaments.
To make the Santa Hats, pipe red frosting around the base of the kiss and on top.