Preheat the oven to 350 degrees F. Lightly grease an 8x8 pan with baking spray or butter.
Coarsely chop 1 cup of the malted milk balls (slicing some in half and/or leaving a few almost whole is fine; it will add texture to the blondies). Chop the remaining 1/2 cup into smaller pieces; this will be the topping.
In a small bowl, whisk together the flour, malted milk powder, and salt.
In a large bowl, beat the butter and brown sugar with an electric mixer (or use a stand mixer with the paddle attachment) until very smooth, 1-2 minutes. Mix in the egg and vanilla for an additional minute.
Fold in the flour mixture followed by the coarsely chopped malted milk balls until no flour patches remain.
Spread the batter evenly into the prepared pan. Sprinkle the remaining chopped milk balls evenly on top.
Bake for 20-23 minutes, or until the edges are starting to brown but the center isn’t completely set (they’re similar to brownies; better to slightly undercook them as opposed to drying them out).