A fairly simple task I thought - chocolate, peanut butter, sugar. Reese's list the ingredients as milk chocolate, peanuts, sugar, salt (& preservative).
The only other Instructable I could find like this is this one. The method of construction is different, but probably a bit easier if you don't want the classic cup-shape.
Thank you for the peanut butter cups, i have just eaten one, it was lush. X(verdict by SMS)
Step 1: Ingredients & Other Materials
~100g Icing-sugar, otherwise known as confectioner's sugar. This packet is white powdered refined cane-sugar.
~100g Peanut butter (smooth). This jar claims the ingredients to include 92% roasted peanuts and some salt. Yes the label does advise that it "Contains peanuts."
~200g Chocolate. Use what you like, I went for "Chocolate flavour cake covering", as this is the sort of thing my sister likes.
For making the cups, I used some "white baking cases", an improvised bain-marie and a few other common kitchen tools.
Step 2: Stage 1 - Hollow Chocolate Cups
Melt the chocolate in whichever way works for you. I improvised a bain-marie by sitting a bowl on top of a pan simmering water gently.
Add a spoon of molten chocolate to a baking case, and push it up the sides with a small spoon. It will relax back down to the bottom, leaving a coating on the sides. Leave the chocolate to cool and move on to the next case.
Step 3: Stage 2 - Peanut Butter Filling
To fill the cups - warm the filling, but only warm it, to around body temperature.
I found the mixture to be thixotropic i.e. it would liquefy to an extent if shaken, so one blob in each cup, a bit of a shake and the filling settled nicely.
Step 4: Finish
With a bit of practice I could do better, and so could anyone else. But the things worked, I ate one it was just fine (and I don't really like these things).
I made 10 cups from the ingredients, they'll be ~40g (twice the Reese's) ~200 kcal.: they are high in fat and sugar.