Line a 12-well muffin tin with paper liners and set aside
In a small bowl combine the peanut butter, collagen powder, honey and vanilla, stirring until smooth. Set aside in the fridge
Place the chocolate in a microwave-safe bowl and heat on 60% power in 1-minute increments, stirring between cooking times, until all the chocolate has melted, or 3–4 minutes. Alternatively, melt the chocolate in a metal bowl set over a pot with a few centimetres of simmering water on the stove, stirring until smooth. (Be sure not to get any steam or water in the chocolate or it will seize.)
Spoon about 1 tsp of the chocolate into the paper liners, spreading the chocolate to the edges. Using a 1/2 tsp measure, put a heaping spoonful of the peanut butter mixture in the centre of each muffin cup.
Spoon the remaining chocolate over the peanut butter, about 2 tsp per muffin cup.
Refrigerate until the chocolate is set, about 4 hours.
Remove the peanut butter cups (still in their liners) from the muffin tin and store in the fridge in an airtight container for up to two weeks.