Begin by placing the softened butter and both types of sugar (granulated and brown) into the bowl of your stand mixer fitted with the paddle attachment. Mix on medium-high speed for about 3 to 4 minutes until the mixture is creamed and light in color. It should be fluffy and smooth—this is where the magic begins.
Next, stop the mixer and scrape down the sides of the bowl. Add the egg and vanilla extract. Beat on medium-high speed for another 2 minutes until everything is well combined. The batter should look creamy and cohesive.
Now, it's time to incorporate the cream. With the mixer still running, add it in and blend for about a minute. The batter may appear a bit grainy at this stage; don’t worry, it’s perfectly normal.
Reduce the mixer speed to low and add the flour, cocoa powder, baking soda, and salt. Mix until just combined, which should take about 1 minute. Be careful not to overmix; we want soft cookies!
Once combined, scrape down the sides of the bowl again and add in the semi-sweet chocolate chips. Mix on low speed for an additional 30 seconds, ensuring the chocolate is evenly distributed throughout the dough.
Using a 2-tablespoon cookie scoop or your hands, form approximately 19 equal-sized mounds of dough. Remember, the dough will be soft, so handle it gently. Place the mounds on a large plate or tray.
Cover the tray with plastic wrap and refrigerate the dough for at least 3 hours. You can chill it for up to 5 days if you're planning ahead. This step is crucial for achieving the right texture; unchilled dough will spread too much while baking.
Once you're ready to bake, preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper or a silicone baking mat. This will prevent sticking and help with even baking.
Take the chilled dough mounds out of the refrigerator and flatten them slightly with your palm. Space them at least 2 inches apart on the prepared baking sheet, as they will spread while baking. I usually bake 8 cookies per sheet to ensure even cooking.
Bake the cookies for about 8 to 10 minutes, or until the edges are set and the tops look just set, even if they’re slightly undercooked in the center. This is key for that soft, chewy texture. Don’t overbake; cookies will firm up as they cool.
After baking, allow the cookies to cool completely on the baking sheet. I prefer to leave them on the sheet rather than transferring them to a rack.
While the cookies are cooling, prepare the ganache. In a medium bowl, add the chocolate chips and set aside. In a microwave-safe measuring cup, heat the cream on high power until just boiling, which should take about 30 seconds. Keep an eye on it to avoid boiling over.
Pour the hot cream over the chocolate chips and cover the bowl with plastic wrap or foil to trap in the heat. Let it sit for about 10 minutes. This allows the chocolate to melt.
After 10 minutes, whisk the ganache mixture until smooth. If the chocolate chips haven’t melted completely, you can microwave the bowl for an additional 15 to 30 seconds. This should help create a silky ganache.
To finish, add about 1 to 2 tablespoons of ganache to the top of each cooled cookie. Use a spoon or offset spatula to spread it evenly. Finally, sprinkle with sprinkles for a fun and festive touch!