Preheat oven to 350°F (175°C) and line baking sheets with parchment paper or silicone mats.

In a large bowl, whisk melted butter with granulated and brown sugar until smooth and slightly lightened.

Beat in eggs, vanilla extract, and peppermint extract (if using) until the mixture is glossy.

In another bowl, whisk cocoa powder, flour, baking powder, and salt; then pour into wet ingredients and stir until just combined.

Gently fold in chocolate chips and optional sprinkles, taking care not to overmix the dough.

Scoop dough onto a tray and chill in the fridge for 15–20 minutes to prevent excessive spreading.

Bake chilled dough for 10–12 minutes—edges should be set while centers remain soft.

Let cookies rest on the pan for 5 minutes before transferring to a wire rack to cool completely.