Chocolate-Oatmeal Moon Pies

Arrange racks in upper and lower thirds of oven; preheat to 350 °F. Line 3 baking sheets with parchment paper. Whisk flour, baking powder, baking soda, and salt in a medium bowl. Combine oats, cherries, pecans, and chocolate in a large bowl. Using an electric mixer, beat butter and sugar in another large bowl, occasionally scraping down sides of bowl, until smooth, about 2 minutes. Add egg and vanilla and beat to blend. Scrape down sides of bowl. With machine running at low speed, gradually add flour mixture; beat just to blend. Stir in oat mixture with a wooden spoon just to blend. Using a 1-ounce ice cream scoop or scooping out 2 level tablespoonfuls of dough, measure dough into 36 portions. Divide among baking sheets. Using your hands, gently press down on each dough ball until 1/2" thick. Bake cookies for 12 minutes. Rotate sheets front to back and top to bottom; continue baking until cookies are golden brown and edges have begun to set but centers are still soft (cookies will appear underdone and shiny in centers), 7-8 minutes longer. Do not overbake. Let cookies cool on baking sheets. DO AHEAD: Cookies can be made 2 days ahead. Store airtight at room temperature. Spread 1 tablespoon marshmallow creme on bottom of 18 cookies. Sandwich with remaining cookies.