Preheat the oven to 375°F (190°C). Butter or spray a baking sheet or line with parchment paper.
Melt the chocolate: start with 8 ounces semisweet chocolate in a microwavable or glass bowl. You can use the microwave (short 10-15 second spurts stirring well between each one until it's fully melted) or a double boiler with the bowl containing the chocolate not touching the water. In both cases, make sure it doesn't scorch.
Beat 1 cup unsalted butter with ¾ cup white sugar and ½ cup brown sugar in a large bowl for about 3 minutes, until creamy.
Add 2 eggs, one at a time, beating well after each addition. Scrape the sides of the bowl each time.
Add the melted chocolate, 1 ½ teaspoons vanilla extract, ½ teaspoon mint extract and mix until smooth.
Sift the dry ingredients (2 ½ cups all-purpose flour, 4 tablespoons unsweetened cocoa powder, 1 teaspoon baking soda and ½ teaspoon salt) before adding them to the butter mixture, or have them measured and sift as you add them. Don’t overbeat at this point. Simply mix well with a spatula or beat at the lowest speed until no streaks of flour remain.
Add 1 cup semisweet chocolate chips and ⅔ cup crushed peppermint candy cane. Mix well. At this point, you can bake the cookies or cover the bowl and refrigerate the cookie dough for a day or two.
Scoop portions on the prepared baking sheets making sure they're separated 2 inches from each other.
Sprinkle with extra crushed candy cane if you want to. They look prettier after they're baked.
Bake for 10 minutes, until the edges are dry but the centers are still soft.
Let cool on a wire rack for about 5 minutes and carefully remove from the sheets and let cool completely on the cooling racks.
Store in an airtight container or cookie jar.