Line a 20 count mini muffin tin or 12-count standard muffin tin with muffin liners and set aside.
Set aside half a cup of the white chocolate chips. In a microwave-safe bowl or stovetop, melt the 3 1/2 cups remaining chocolate chips until smooth and silky. Moving quickly, distribute the melted white chocolate amongst the lined muffin cups, scraping down the sides. Once it is all done, place in the freezer.
While the white chocolate cups are freezing, start preparing your peanut butter filling. Add your peanut butter and flour and mix well. Using a tablespoon, add milk of choice until desired texture remains.
Remove chilled white chocolate cups from the freezer and evenly distribute the peanut butter filling amongst them all. Once it is all used up, melt the remaining half cup of white chocolate chips and pour to cover each of the cups. Refrigerate until firm.
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Notes
TO STORE. Keep leftovers in the fridge to prevent them from softening. They will keep well for a week and even longer stored in an airtight container. Layer the cups using parchment paper to prevent them from sticking to each other. TO FREEZE. These cups freeze well for up to 3 months. For the best results, wrap each cup with food wrap and store them in an airtight container or freezer bag.