Preheat oven to 350 degrees F. In a large bowl beat shortening and peanut butter with a mixer on medium to high 30 seconds. Add the 1/2 cup granulated sugar, the brown sugar, baking powder, salt, and baking soda. Beat until combined, scraping bowl as needed. Beat in egg, milk, and vanilla until combined. Beat in flour.
Shape dough into about 1-inch balls. Roll balls in the 2 Tbsp. granulated sugar. Place 2 inches apart on an ungreased cookie sheet. Flatten slightly making crisscross marks with fork tines. Bake 7 to 9 minutes or until edges are firm and bottoms are light brown. Remove; cool cookies on wire rack.
For each sandwich cookie, spread bottom of one cookie with 1/4 to 1/2 tsp. jelly and, if desired, the bottom of another cookie with 1/4 to 1/2 tsp. peanut butter. Place one cookie on top of another, pressing together lightly.