Start by melting butter in a small saucepan over medium heat. Add brown sugar, salt, vanilla, and bourbon, then whisk until everything blends together smoothly.

Continue cooking while stirring until the mixture thickens and reaches a caramel-like consistency. Pour it onto parchment paper and allow it to cool before chopping into small pieces.

Preheat your oven to a low temperature and line a baking tray with parchment paper. In a bowl, combine crushed cornflakes, milk powder, sugar, and salt.

Pour melted butter over the mixture and toss until the flakes are evenly coated. Spread the mixture on the tray and bake until golden and crunchy.

Place butter in a saucepan over medium heat and cook until it melts and begins to turn golden brown. Stir continuously so the butter does not burn.

Once it develops a nutty aroma and deep color, remove it from heat and allow it to cool slightly before using.

Mix the cooled brown butter with dark brown sugar and granulated sugar until smooth. Add the egg, egg yolk, and vanilla extract, then beat until creamy.

In another bowl, whisk flour, baking soda, baking powder, and salt. Combine the dry ingredients with the wet mixture until a soft dough forms.

Fold the prepared cornflake crunch and chopped toffee pieces into the cookie dough. Mix gently so the crunchy pieces remain intact.

Scoop large portions of dough and chill them in the refrigerator overnight or at least eight hours.

Preheat the oven and place the chilled dough balls on a lined baking tray with space between them. Bake until the edges turn golden while the centers stay soft.

Let the cookies cool for a few minutes, then sprinkle with extra cornflakes, toffee pieces, and edible glitter for a beautiful sparkling finish.