1-First, preheat the oven to 350°F (177°C) and line cookie sheets with parchment paper. Cut the butter into tablespoon-sized pieces and melt it over medium-low heat, then increase to just above medium while swirling and scraping the pan sides frequently.

2-Browning and Mixing the Ingredients: When the butter begins to brown and smells nutty, remove it from the heat and pour it into a heatproof bowl, letting it cool for 25-30 minutes. Add the brown sugar and white sugar to the cooled browned butter and stir well, then mix in the eggs one at a time, followed by the vanilla extract.

3-In a separate bowl, whisk together the all-purpose flour, cornstarch, baking powder, baking soda, and salt. Gradually fold the dry ingredients into the wet mixture until nearly combined, then fold in the milk chocolate toffee pieces evenly.

4-Baking and Finishing Touches: Scoop and roll the dough into 1 ½ tablespoon balls, placing them on the parchment-lined sheets at least 2 inches apart. Bake for 9-10 minutes until the edges turn golden brown, with the centers remaining slightly soft. Sprinkle lightly with sea salt while the cookies are warm, cool on the pan for 3 minutes, and transfer to a rack to cool completely.