Peanut butter cups are easy to make at home and a fun activity for kids.
Line a sheet tray with parchment paper and sprinkle confectioner’s sugar evenly over the parchment. Set aside.
Place the egg whites in a stand mixer with the whisk attachment. In separate saucepans, mix 1 cup of sugar with a small amount of water, and 1 ¾ cups of sugar with a small amount of water. Place both pans over medium heat and bring to a boil.
When the 1 cup of sugar comes to a boil, begin whipping the egg whites. Using candy thermometers, measure the temperature of both saucepans. When the 1 cup of sugar reaches 240 degrees, pour it into the whipping whites; lower the speed of the white to ensure the hot sugar does not splash out of the bowl. Once all of the sugar mixture is poured in, increase the speed and continue whipping.
When the 1 ¾ cups of sugar reaches 254 degrees, pour it into the whipping egg whites/sugar mixture (again, be sure to lower the speed until all is poured in). Continue to whip for 1 minute, then remove from the stand mixer and stir in the peanut butter by hand just to combine.
Spread the filling onto the prepared pan and let sit at room temperature.
Line a mini-muffin pan with mini cupcake liners. Set aside.
Line a second sheet tray with parchment. Using your hands, form small discs of the filling, about the circumference of the cupcake liners. Place the discs onto the second sheet tray.
Melt chocolate with the butter in a bowl over a double boiler until almost fully melted, stirring to heat evenly. Ensure the mixture is smooth and there are no chunks of chocolate left.
Pour some chocolate into each cupcake liner, so each is approximately 1/3 full. Place a disc of filling into each cupcake liner and lightly press down. Pour additional melted chocolate over each peanut butter cup to cover the filling. Refrigerate until firm, approximately 30 minutes. Remove hardened peanut butter cups from muffin tin. Store in the refrigerator until ready to serve.