Chop the dark chocolate with a knife and put it in a plate together with 75 g of natural peanut butter.
Melt in the microwave for 2 minutes at 800 W, stirring every 30 seconds.
Grease and line the 21×9 mold with parchment paper making it adhere perfectly and pour 130 g of the chocolate and peanut butter mixture that you just obtained.
Beat the mold well on the table to create a homogeneous base, then place in the refrigerator to cool for 20-30 minutes.
Meanwhile, chop the white chocolate with a knife and put it in a plate together with the remaining 60 g of peanut butter.
Melt in the microwave at 600 W for 2 minutes, stirring every 30 seconds.
Once the first layer of chocolate is solid, pour a second layer of white chocolate over it. Beat the mold well and refrigerate for another 20-30 minutes.
Finally, cover with the last layer of dark chocolate, pouring the other half of the mixture over the white layer. Beat well and refrigerate for 1 hour.
Then cut into cubes or rectangles and serve!