To a large mixing bowl, add butter, flour, sugar, brown sugar, salt, baking powder, vanilla, and milk. Mix together and set aside.
In a small food processor, add the malted milk ball candy. Use the chop setting to process the candy.
Pour the malted milk ball candy in the large bowl and stir into the cookie dough.
Using your hands, knead the dough just a bit to form a large round and set it on a plate. Roll the dough into small balls (just a little smaller than a whole walnut). Set aside.
For the Chocolate Coating:
Line a cookie pan or large flat platter with wax paper (after dipping the cookie dough balls in chocolate they'll need to chill in the fridge; using several medium-size flat plates instead of a large pan/platter may be easier to fit in your fridge)
In a small microwavable bowl, add the melting chocolate. Warm in the microwave for about 45 seconds and then stir. Warm for another 30 seconds (or more if needed) and stir until the chocolate is smooth.
Dip a cookie dough ball in the melted chocolate so that all sides are covered in chocolate. Using a small spoon, lift the cookie dough ball from the chocolate and let the excess chocolate drip back into the bowl.
Transfer the truffle on to the wax paper and top with candy sprinkles. Repeat for the rest of the cookie dough balls. Coating the dough balls one at a time works best so that the candy sprinkles can be added immediately after applying the chocolate so that the candy will stick.
Let chill in the refrigerator until the chocolate sets (about 30 minutes). Serve chilled or at room temperature. Store leftover truffles in the refrigerator.
After dipping the cookie dough balls in chocolate they'll need to chill in the fridge; using several medium-size flat plates instead of a large pan/platter may be easier to fit in your fridge.
Coating the dough balls with chocolate one by one, and adding the candy sprinkles right afterwards works best because the candy can adhere to the chocolate while it's still soft. The candy sprinkles won't stick to the chocolate once it starts to harden (which happens fairly quickly).