Line a small baking pan with parchment and set aside.

In a small pot, melt the butter on medium heat.

Add light brown sugar, salt, vanilla, and bourbon. Whisk vigorously for about a minute until fully combined.

Keep cooking the mixture, stirring constantly, until it thickens and bubbles. Use a candy thermometer to ensure it reaches 295 - 305 degrees Fahrenheit.

Quickly pour the liquid toffee onto the lined baking sheet and spread it if desired. Let it cool for about 15 minutes until hard, then chop into small pieces.

Preheat the oven to 275 degrees and line a medium baking sheet pan with parchment.

In a bowl, combine cornflakes, milk powder, white sugar, and salt. Toss until combined.

Pour in the melted butter and toss until cornflakes are coated.

Spread the cornflake mixture evenly on the baking sheet and bake for about 20 minutes until golden. Let cool and break up any big pieces.

To make brown butter, place unsalted butter in a light-colored pot over medium heat and melt. Stir constantly for 5 to 8 minutes until golden brown and nutty aroma is released. Set aside to cool.

In a medium bowl, combine cooled brown butter, dark brown sugar, and white sugar. Beat with an electric mixer until combined.

Add in the egg, egg yolk, and vanilla extract. Beat until smooth and combined.

In a separate bowl, whisk together all purpose flour, bread flour, baking soda, baking powder, and sea salt.

Gradually fold in the dry flour mixture until no dry pockets remain.

Add in the cornflake crunch mixture and chopped toffee pieces. Mix until fully combined.

Scoop the dough into 4 tablespoon balls and chill in the fridge for a minimum of 8 hours, or overnight.

Preheat the oven to 350 degrees and line a baking pan with parchment paper. Place 5 cookie dough balls on the tray, leaving 2 inches of space between each ball.

Bake the cookies for about 9 - 10 minutes, just until the edges are golden brown. Smack the pan against the counter to encourage rippling.

Top each cookie with reserved cornflakes and toffee pieces. Let cool for about 10-15 minutes.

If desired, sprinkle edible gold glitter on top before serving.