In a large bowl toss puffed rice with cocoa powder and set aside.

Pour milk into a saucepan, add butter and sugar and bring to a boil, stirring constantly. When the mixture starts to bubble, cook for 1-1,5 minutes, whisking constantly.

Remove the pan from the heat and stir in dark chocolate. Mix well until the mixture becomes smooth and homogeneous. Let cool for 15 minutes.

Meanwhile, line a baking tray with parchment paper or silicone mat.

When the chocolate mixture is no more hot, pour it over puffed rice and mix well.

Using 2 spoons, scoop the mixture onto the baking tray. Press the dough with a spoon to form a cookie round.

Let the cookies sit at room temperature for 30 minutes, then transfer to the fridge to firm.

Serve and enjoy!