FOR THE COOKIES: Heat oven to 350 degrees Fahrenheit. Whisk flour, baking powder, and salt in a medium bowl until combined.
With an electric hand mixer, cream the shortening and sugar in a large bowl on high speed until light and fluffy.
Add the egg, milk, and vanilla. Mix to combine. Gradually blend in flour mixture.
Divide dough in half. Roll out each half on a lightly floured surface 1/4-inch thick for crisp cookies, or 3/8-inch thick for softer cookies. Cut with 2 to 3-inch cookie cutters. Place 2-inches apart on a parchment/silicone lined baking sheet.
Bake for 8-9 minutes, until edges are just starting to brown. Remove from oven. Rest on cookie sheet for 1-2 minutes, then and transfer to a cooling rack.
FOR THE FROSTING: With an electric hand mixer, cream the shortening, brown sugar, cinnamon, and vanilla in a large bowl. Gradually add powdered sugar while mixing. Add milk 1 Tbsp at a time until desired consistency.
TOAST PECANS in a saute pan over medium-high heat until fragrant, about 2-5 minutes, stirring continually. Cool and chop half of the mixture.
Pipe or spread frosting on top of the cooled cookies. Place one whole pecan on top in the center of the frosting, followed by sprinkling a few chopped nuts. Store in an airtight container at room temperature.