Add 1 stick of butter to a small saucepan set over medium heat. Cook until the butter begins to brown, about 3-4 minutes. Remove from the heat and transfer to a heatproof bowl. Stick in the freezer to chill, 10-15 minutes, but no longer.Preheat the oven to 350° F. Line a baking sheet with parchment paper.In a large mixing bowl, beat together the remaining stick of butter, the cooled browned butter, brown sugar, and granulated sugar until combined. Beat in the eggs, 1 at a time, until combined. Add the vanilla, beating until creamy. Add the flour, malted milk powder, baking soda, and salt. Fold in the chocolate chunks.Roll the dough into rounded 1 tablespoon size balls and place 3 inches apart on the prepared baking sheet. Transfer to the oven and bake for 7 minutes. Remove the pan from the oven and tap the baking sheet on the counter 2 times to flatten them down. Return to the oven and bake another 1-3 minutes or until the cookies are just beginning to set on the edges, but still doughy in the center. Remove from the oven and tap the baking sheet on the counter 1-2 times to flatten them down again. Let the cookies cool on the baking sheet. They will continue to cook slightly as they sit on the baking sheet. Sprinkle with flaky salt (if desired). Eat warm (highly recommended) or let cool and store in an airtight container for up to 4 days.