Preheat the oven to 350°F. Line a 9x9-inch baking pan with parchment paper, leaving an overhang for easy removal.
Melt 0.5 cup of chocolate chips with vegetable oil in the microwave in 15-second intervals, stirring until smooth. Let cool slightly.
In a stand mixer, beat granulated sugar, brown sugar, eggs, vanilla extract, and peppermint extract on high speed for 5-6 minutes until pale and thick.
Slowly mix melted chocolate mixture into the wet ingredients on low speed until just combined.
Whisk together flour, cocoa powder, and kosher salt in a small bowl.
Add the dry ingredients to the wet ingredients and mix on low speed until just combined.
Fold in the remaining 0.75 cup of chocolate chips.
Pour batter into the prepared pan and smooth the top. Sprinkle remaining chocolate chips evenly over the batter.
Bake for 30-35 minutes or until a toothpick inserted near the center comes out with moist crumbs but no wet batter.
Immediately sprinkle crushed peppermint candies over the hot brownies. Cool completely in the pan on a wire rack.
Lift brownies from the pan using parchment overhang. Cut into squares and serve.
Notes
Store brownies in an airtight container at room temperature for up to 5 days. For a festive touch, serve with whipped cream or vanilla ice cream.