Dark chocolate peanut butter cups

The measurements here don't have to be that precise, since there is no actual baking involved.

350g / 12 oz (about 2 cups) smooth peanut butter
1 cup of salted roasted peanuts
225g / 8oz (about 1 cup) icing sugar
50g / 1.8oz (about 1/4 cup) brown sugar, or raw sugar (Rohzucker)
500g / a bit more than a pound, or 5 bars, of dark chocolate, minimum cacao 50% (I used Cailliers Cremant)
90g / 3oz unsalted butter
Supplies needed: shallow paper cake/muffin cups (use regular cake cups if you can't find shallow ones), plastic zip bag

Chop up the peanuts with a knife or in the food processor until they are as fine as you'd like them to be.
Put the peanut butter, 60 grams/2 oz (2/3rds of the) butter, peanuts, and both sugars in a sturdy plastic zip bag.

Press the air out of the bag and close it. Knead and mix the bag until the contents are completely mixed and smooth.

Once the mixture is mixed, press down the mixture towards one corner. Cut off the corner with scissors, and twist the bag - now you have a sort of pastry bag.
Squeeze about a tablespoon worth of the peanut butter mixture into each paper cup, smoothing out the top of each with your finger. Each cup should be about 1/2 full. It's easier if you keep each cup in the stack of other paper cups for stability while you fill them.
Once the peanut butter mixture is all used up, make the chocolate topping. Break up the chocolate into a bowl or a soup plate (the soup plate will allow for faster melting since the chocolate is more spread out). Melt it in the microwave at medium for about 3 minutes. Check at this point; if the chocolate is still hard, mix and nuke for about 1 minute more. Add the rest of the butter, and nuke for another 30 seconds. Mix the chocolate and butter well with a spoon until smooth.
Fill up each cup with the chocolate, smoothing out the top with a knife.

Cool in the refrigerator until the chocolate is firm, about 1 hour. Makes about 24 cups.

Note: if you would rather not put in peanuts, increase the amount of peanut butter by about 1/2 cup, and add about 1/2 teaspoon of salt. You can also use chunky style peanut butter increasing the amount by about 1/2 cup.