Make the cookies
In a medium bowl, whisk the flour, baking powder, and salt. In a stand mixer fitted with the paddle attachment, beat the butter, sugar, and cocoa powder on low speed until blended; then raise the speed to medium and beat until light and fluffy, about 3 minutes. Scrape down the bowl and beater. Add the egg yolks and vanilla and mix on medium speed until well blended, about 1 minute. Add the flour mixture and mix on low speed until the dough comes together, about 1 minute.
Turn the dough out onto a work surface and divide into 3 equal piles on pieces of plastic wrap. Using the plastic as an aid, gently shape each one into a smooth, flat 5-inch disk and wrap in the plastic. Refrigerate until chilled, about 30 minutes. (The dough can be refrigerated for up to 3 days or frozen for up to 1 month.)
Position a rack in the center of the oven and heat the oven to 375°F. Line 2 cookie sheets with parchment or nonstick baking liners.
Working with one disk at a time, roll the dough between two sheets of lightly floured parchment or on a floured work surface until 1/8 to 3/16 inch thick. Dust with additional flour as needed. Using a 2-1/4-inch cookie cutter, cut out shapes. Arrange about 1 inch apart on the lined cookie sheets. Stack the scraps and gently press them together. Re-roll and cut. Repeat with remaining dough disks.
Bake, one sheet at a time, until the cookies look dry and slightly cracked and feel somewhat firm when pressed, 7 to 9 minutes. Let cool on the sheet for about 5 minutes and then transfer to a rack to cool completely. (The cookies can be stored in an airtight container at room temperature for up to 5 days or frozen for up to 1 month before filling and glazing.)
Fill the cookies
Press the preserves through a fine sieve, discarding any large pieces of apricot. Arrange half of the cookies bottom side up on a work surface. Put 1 tsp. of the preserves in the center of each cookie. Cover each with one of the remaining cookies, bottom side down. Gently squeeze each cookie together to spread the preserves until it just reaches the edges.
Glaze the cookies
Line 2 or 3 baking sheets with parchment, aluminum foil, or waxed paper. Put the chocolate and oil in a small, deep, heatproof bowl. Heat in a microwave until almost melted, or set the bowl in a skillet of barely simmering water and stir until melted and smooth.
Dip each cookie halfway into the glaze until lightly covered. Lift the cookie out and gently scrape the bottom against the side of the bowl to remove excess glaze. Set on the prepared baking sheets. Let the cookies sit at room temperature or in the refrigerator until the glaze is firm. Serve immediately or store in an airtight container at room temperature for up to 2 days.
nutrition information (per serving):
Photo: Scott Phillips