Preheat the oven to 375F (190C) and place a rack in the top 1/3 of the oven, at least 6-inches from the heat source. Grease a regular muffin tin or use muffin liners. *Ideally only fill every other muffin well and your cupcakes will get more rise.
In an electric stand mixer fitted with the paddle attachment beat the butter, granulated sugar, brown sugar on high until smooth and lump free, about 4-5 minutes. Scrape down the sides and bottom of the bowl periodically so that everything is well mixed together. With the mixer on low add the eggs one at a time, mixing the first completely before adding the second. Finally add in the vanilla and mix until smooth and combined. Take the bowl out of the mixer.
In a medium bowl whisk together the flour, malted milk powder, cocoa powder, baking soda, baking powder and sea salt. Alternate adding the flour mixture and the buttermilk into the butter mixture in two batches, ending with the buttermilk. Stir until barely combined and you still see streaks of flour. Fold in the chopped Alter Eco Deep Dark Salt & Malt Bar. Scoop the batter into the muffin liners and fill until a generous ¾ full. Let the muffins sit for 15 minutes before putting in the oven; this helps them get a wee more rise (and is optional).
Bake for 17 minutes in the top third of the oven or until a toothpick comes out clean or they bounce back when gently pressed in the center. For best results, bake one tin at a time.
Let cool in the muffin tin for about 10ish minutes, then use a butter knife to help get them out to finish cooling on a rack.