Place 1/2 cup heavy cream and 3 tablespoon unsalted butter in a small saucepan over medium heat. Heat, stirring occasionally, until the butter melts and the cream barely comes to a boil, about 3 minutes. Add 1/3 cup granulated sugar and 1/3 cup packed dark brown sugar and stir until dissolved.

Reduce the heat to low. While whisking constantly, add 1/2 cup unsweetened Dutch-process cocoa powder and a pinch of kosher salt, and whisk until combined. Remove the saucepan from the heat and let cool for 3 to 5 minutes. Serve warm over a scoop of your favorite ice cream, or whisked into a glass of milk to create rich chocolate milk.

As the syrup cools, the consistency will thicken. After 10 minutes, the texture will resemble brownie batter in thickness and color. Once it’s completely cooled, it will resemble a thick ganache.