Prepare the oven and baking pan

Preheat the oven to 325°F (165°C). Line a 9 x 13-inch (23 x 33 cm) metal baking pan with parchment paper, leaving an overhang on two opposite sides. This will help lift the bars out after cooling. Keep the pan ungreased beneath the parchment.

Drain and dry the cherries

Place the maraschino cherries in a fine-mesh strainer and allow the syrup to drain. Pat them thoroughly dry with paper towels, then finely chop them. Blot the chopped cherries again to remove any newly released moisture. The pieces should feel slightly tacky rather than wet or dripping.

Cream the butter and sugar

In a large mixing bowl, beat the softened unsalted butter and powdered sugar with an electric mixer on medium speed for about 2 minutes. Scrape down the sides of the bowl as needed. The mixture should look smooth, creamy, and slightly lighter in color, but it does not need to become extremely fluffy.

Add the flavorings

Mix in the vanilla extract and almond extract on low speed until evenly incorporated. The butter mixture should remain smooth and creamy.

Combine the dry ingredients

In a separate bowl, whisk together the all-purpose flour and fine salt. Add the dry mixture to the butter mixture in two additions, mixing on low speed just until the flour disappears. The dough will be thick, soft, and somewhat crumbly, but it should hold together when squeezed. If it looks sandy, press a small portion together before deciding it needs more mixing.

Fold in the cherries and chocolate chips

Add the ¾ cup (120 g) chopped, dried maraschino cherries and ¾ cup (130 g) mini semisweet chocolate chips. Fold them into the dough with a rubber spatula until evenly distributed. Avoid excessive mixing, which can crush the cherries and streak the dough pink.

Press the dough into the pan

Transfer the dough to the prepared baking pan: Distribute it in small portions across the pan, then press firmly into an even layer using your fingers or the flat bottom of a measuring cup. Pay attention to the corners so the bars bake evenly. If using the optional topping, sprinkle the remaining 2 tablespoons (22 g) mini chocolate chips over the surface and press them in lightly.

Bake until lightly golden

Place the pan on the center oven rack and bake for 30 to 35 minutes. The edges should be lightly golden, and the center should look set and matte rather than shiny or wet. Shortbread remains fairly pale across the top, so do not wait for deep browning. If the edges are coloring too quickly, loosely cover the pan with aluminum foil for the final few minutes.

Cool the shortbread completely

Transfer the pan to a wire rack and let the bars cool in the pan for approximately 1 hour 30 minutes. The shortbread will firm as it cools. Avoid lifting or cutting it while hot because the delicate crumb may break apart.

Slice and serve

Once completely cool, use the parchment overhang to lift the shortbread onto a cutting board. With a sharp knife, cut into 24 bars using a 4-by-6 grid. Wipe the knife between cuts if chocolate or cherry pieces stick to the blade. Serve at room temperature.