In a mixing bowl, combine flour, sugar, and cold unsalted butter. Use your fingertips to rub the ingredients together until the mixture resembles breadcrumbs. Roll this out thinly, freeze until firm, and cut into discs for topping.

In a saucepan over medium heat, combine milk, water, butter, sugar, and salt. Bring to a boil, then stir in the flour, mixing vigorously. Add eggs one at a time, stirring until the dough is smooth and glossy.

Transfer the dough to a piping bag fitted with a round tip. Pipe small rounds onto parchment-lined baking sheets, leaving space between each. Place a frozen crumble disc atop each piped round gently.

Preheat your oven to 340°F (170°C). Bake for 30-35 minutes until puffed up and golden brown. Allow them to cool completely on a wire rack.

Heat the milk in a saucepan. In a mixing bowl, whisk together egg yolks, sugar, and cornstarch until smooth. Gradually whisk the hot milk into the mixture and return it to the saucepan. Stir over low heat until the cream thickens; chill afterward. Fold in whipped cream before filling the puffs.

In a small saucepan, combine sugar and water over medium heat. Allow it to cook until it reaches a deep amber color. Quickly dip the tops of your filled puffs into the hot caramel, letting any excess drip off.

Drizzle extra chocolate over the tops for a delightful surprise!