Step 1: Preheat your oven to 200°C (400°F). Line a baking sheet with parchment paper and draw a 20cm (8-inch) circle on it. Flip the paper over so the pencil mark is underneath.
Step 2: For the Choux Pastry: In a saucepan, combine 125 ml whole milk, 125 ml water, 100 g unsalted butter, 1 tsp sugar, and ½ tsp salt. Bring to a rolling boil over medium heat.
Step 3: Remove the pan from the heat and immediately add 150 g plain flour all at once. Stir vigorously with a wooden spoon until the mixture forms a ball and leaves the sides of the pan clean. Return to low heat and cook for another 1-2 minutes, stirring constantly, to dry out the dough.
Step 4: Transfer the dough to a large bowl (or stand mixer). Beat in 4 large eggs, one at a time, ensuring each egg is fully incorporated before adding the next. The dough should be smooth, glossy, and thick enough to hold its shape when piped.
Step 5: Transfer the choux pastry to a piping bag fitted with a large star nozzle. Pipe a ring of choux onto the prepared baking sheet, following your drawn circle. Pipe a second ring on top of the first, and a third ring inside the first, nestling against it, to create a sturdy base.
Step 6: Bake the choux ring for 20 minutes at 200°C (400°F). Reduce the oven temperature to 180°C (350°F) and bake for another 15-20 minutes, or until deeply golden brown and firm. Do not open the oven door during the first 25 minutes. Once baked, turn off the oven, prop the door ajar, and let the choux cool completely inside for about 30 minutes to prevent it from deflating. Once cool, slice the choux ring horizontally in half with a serrated knife.
Step 7: For the Honey-Hazelnut Praline Cream: Spread 100 g toasted hazelnuts on a baking sheet and set aside. In a saucepan, combine 80 g sugar and 20 g honey with 1 tbsp water. Heat gently until the sugar dissolves, then increase heat to medium-high and cook until the mixture turns a deep amber caramel. Add the toasted hazelnuts and stir to coat. Pour onto a parchment-lined baking sheet and spread thinly. Let cool completely and harden.
Step 8: Once hardened, break the praline into pieces and process in a food processor until it forms a smooth, runny paste (this takes time and patience).
Step 9: In a bowl, whisk 3 large egg yolks with 40 g sugar and 25 g cornflour until pale and creamy. In a separate saucepan, heat 300 ml whole milk until just simmering. Slowly pour the hot milk into the egg mixture, whisking constantly.
Step 10: Return the mixture to the saucepan and cook over medium heat, stirring continuously, until it thickens into a thick custard. Remove from heat, stir in the hazelnut praline paste, then mix in 120 g softened unsalted butter until fully combined and smooth. Cover the surface with plastic wrap to prevent a skin from forming and chill in the refrigerator until completely cold (at least 2-3 hours).
Step 11: Once the praline cream is chilled, whip 100 ml double cream to soft peaks and gently fold into the praline custard until combined. Transfer to a piping bag fitted with a large star nozzle.
Step 12: For the Chantilly Cream: In a cold bowl, whip 250 ml cold double cream, 1 tbsp honey, and 1 tsp vanilla bean paste until stiff peaks form. Transfer to a piping bag fitted with a large star nozzle.
Step 13: Assembly: Place the bottom half of the cooled choux ring on your serving plate. Pipe the honey-hazelnut praline cream generously onto the choux base. Then, pipe the honey vanilla chantilly cream on top of the praline cream.
Step 14: Carefully place the top half of the choux ring over the creams. Decorate with 50 g roasted chopped hazelnuts and a generous dusting of icing sugar. Serve immediately or chill briefly.