Preheat the oven to 350°F (175°C). Line a 13 × 18-inch (33 × 46 cm) baking sheet with parchment paper. Position an oven rack in the center of the oven for even baking. The parchment will help prevent the chocolate cookies from sticking.

Add the following ingredients to a large mixing bowl: 1 box (18.3 ounces / 519 g) fudge brownie mix, dry mix only 2 large eggs (approximately 100 g without shells), at room temperature 1/4 cup (60 ml) neutral vegetable oil 1/2 teaspoon (2.5 ml) peppermint extract Stir with a sturdy spatula until the dry mix is fully moistened and no powdery streaks remain. The dough should be thick, sticky, and darker than ordinary chocolate chip cookie dough. It should hold a mound rather than flow like brownie batter.

Add 1/2 cup (85 g) semisweet chocolate chips to the dough. Fold gently until the chips are evenly distributed. Scrape the bottom of the bowl to make sure no dry brownie mix remains. Avoid prolonged mixing once the dough is combined. The finished mixture should look thick and glossy, with chocolate chips throughout.

Using a 1 1/2-tablespoon cookie scoop, portion the dough into approximately 24 cookies. Place 5 dough portions on the prepared baking sheet, leaving about 2 inches (5 cm) between them. Keep the remaining dough at room temperature while the first batch bakes. If the dough is sticky, release each portion with the edge of a spoon. Keep the mounds relatively tall rather than flattening them.

Bake at 350°F (175°C) for 11 minutes per batch. The cookies should look slightly puffed, with set edges and soft centers. Small cracks may appear across the surface. The centers should no longer look like liquid batter, but they should still be tender. Do not wait for the entire cookie to become firm in the oven; the cookies continue setting as they cool.

Use 1/3 cup (approximately 50 g) crushed peppermint candy canes, divided; finely crushed with a few slightly larger pieces for texture. Immediately after removing each batch of cookies from the oven, sprinkle a portion of the crushed candy canes over the warm tops, reserving the remaining candy for subsequent batches. Press the candy gently into the surface using the back of a spoon. The cookies should still be soft enough for the pieces to adhere without breaking apart. Concentrate the candy near the centers to create a festive red-and-white finish.

Allow the first batch to rest briefly on the baking sheet before transferring the cookies to a wire rack. Repeat the scooping, baking, and topping process with the remaining dough, for 5 batches total. Use the remaining portions of the divided crushed candy canes to top each batch while the cookies are still warm. Allow the final batch to cool for 10 minutes before serving. The centers will become more stable as the cookies cool while retaining a soft, brownie-like texture.