Preheat oven to 350°F (175°C). Line baking sheets with parchment paper or silicone liners.
Whisk together the flour, baking powder, and salt. Set aside.
Using an electric mixer on medium speed, beat the butter and brown sugar until fluffy. Add the egg and vanilla, mixing until combined. Add 1/2 cup cookie butter, mixing until combined.
Reduce mixer speed to low. Gradually the the flour mixture, mixing just until combined. Stir in the oats, chocolate, nuts, and cranberries.
Drop half the dough by 2-tablespoon portions (I use a #30 scoop) onto the prepared pans. Make a small indentation in the center of each.
Add 1 & 1/2 to 2 teaspoons (I use a #110 scoop) of the remaining cookie butter to the indentation.
Scoop the remaining dough by 2-tablespoon portions. Flatten each portion slightly and place over the cookie bottoms. Pinch the edges to seal, and flatten each cookie slightly.
If you like, top each cookie with more chocolate, nuts, cranberries, and/or oats for garnish.
Bake, one pan at a time, 14 to 16 minutes, or until the edges are golden brown. Cool the cookies on the pan on a wire rack for 10 minutes. Then transfer the cookies to a wire rack to cool completely.
Notes
The dough doesn't need to be chilled before baking unless your kitchen is unusually warm, but I recommend keeping the dough in the refrigerator between batches.