RECIPE PREP: Line 2 baking trays with parchment paper or reusable silicone baking mats. Set them aside.

1. In a large bowl, combine melted butter and light brown sugar. Add large egg and vanilla extract. Whisk until combined. Add flour, malted milk powder, baking powder and sea salt. Stir until all ingredients are fully incorporated, and no large lumps remain.
2. Add malted milk balls and chocolate chunks to the bowl. With a wooden spoon, fold the pieces into the cookie dough. Cover the bowl with plastic wrap and refrigerate for 45 minutes.
3. In the meantime, preheat the oven to 350°F.
4. Once the cookie dough has chilled, scoop round (1.5-tablespoon) balls with a metal scoop. Drop the pucks of dough directly onto the prepared baking sheets. Leave at least 2 1/2-inches between the pieces. To help reduce spread in the oven, chill the trays of dough in the freezer for 10 minutes (or in the fridge for 15 minutes).
5. Bake 10 to 12 minutes, or a bit longer of needed – until the edges are golden blonde. As soon as the treats come out of the oven, press additional pieces of chocolate or malt balls into the cookies, if desired. Sprinkle the tops with a pinch of flaky salt (optional). Allow cookies to cool to room temperature on the baking tray. Then transfer them to a metal rack to finish shedding heat.