Ingredients:
For the Cookie Dough:
1 cup unsalted butter
1 cup + 2 tablespoons light brown muscovado sugar
1 large egg + 1 large egg yolk
1 teaspoon vanilla extract
2½ cups all-purpose flour, plus extra for dusting
1 teaspoon bicarbonate of soda
Pinch of salt
¾ cup milk chocolate chips
Splash of milk
For the Decadent Filling:
1¼ cups chocolate hazelnut spread
⅔ cup white chocolate chips
100g Mini chocolate bars
Instructions:
Make the Cookie Dough Base:
In a large bowl, use an electric hand mixer or a stand mixer with the paddle attachment to beat the softened butter and brown sugar together until the mixture is light, pale, and fluffy.
Add the whole egg and the extra egg yolk, then pour in the vanilla extract. Beat again until the mixture is smooth, creamy, and well combined.
Finish the Dough and Chill:
Add the flour, bicarbonate of soda, a generous pinch of salt, and the milk chocolate chips to the wet mixture. Using a spatula, mix everything together until a stiff dough forms.
If the dough seems too dry and crumbly, add a tiny splash of milk to help it come together.
Divide the dough into two portions:
one about two-thirds of the total, and the other one-third. Pat each portion into a disc about 2cm (¾ inch) thick, wrap them in plastic wrap, and refrigerate for at least 1 hour, or until firm.
Roll and Line the Pan:
Lightly dust a clean work surface with flour. Take the larger disc of dough and roll it out into a round about 23cm (9 inches) in diameter. Carefully transfer the rolled dough to a 20cm (8-inch) springform cake pan. Gently press the dough into the bottom and about 3cm (just over 1 inch) up the sides of the pan, ensuring there are no gaps.
Assemble the Filling:
In a small bowl, stir the chocolate hazelnut spread with a spoon to soften it slightly, then mix in the white chocolate chips.
Spread most of this mixture evenly over the cookie dough base. Press the Mini chocolate bars deeply into the hazelnut spread layer.
Use a small spatula to spread the remaining hazelnut mixture over the bars, creating a relatively even surface. The cookie dough rim should rise slightly above the filling (by about 1cm or ½ inch).
Place the pan in the refrigerator for 20 minutes to firm up the filling.
Seal the Pie:
Remove the smaller disc of dough from the refrigerator. On a lightly floured surface, roll it out into a round about 19cm (7½ inches) in diameter.
Place this dough round on top of the chilled filling, fitting it inside the cookie dough rim. Gently press the edges of the top dough into the rim to seal the filling completely inside the pie.
Return the pie to the refrigerator to chill for at least another hour.
Bake to Golden Perfection:
Preheat your oven to 180°C (350°F), or 160°C (320°F) for a fan-assisted oven. Place the springform pan on a baking sheet to catch any potential drips.
Bake for 50 minutes to 1 hour. Check the pie after about 30-35 minutes; if the top is browning too quickly, loosely cover it with a piece of aluminum foil.
The pie is done when the cookie crust is a deep golden brown and feels set.
Cool and Chill Before Serving:
Remove the pie from the oven and allow it to cool completely to room temperature in the pan on a wire rack.
Once cool, carefully remove the springform ring and base. For the cleanest, most beautiful slices, refrigerate the pie for at least another hour before serving. This allows the chocolate center to set perfectly.