Preheat the oven to 190°C/350°F/Gas Mark 5. Brush the inside of two 18cm (7inch) sandwich cake tins with melted butter and line the base of each tin with a disk of nonstick baking paper. Dust the buttered sides of each tin with flour, shaking out any excess.

Place the butter in a mixing bowl and beat until it has somewhat paled in colour. Add the sugar and beat until light and fluffy. Add the eggs one at a time, beating well between each addition. Sieve the flour and baking powder together, add to the mixture gradually, folding as you go. Finally, add two tablespoons of praline powder and mix everything together lightly, adding milk to moisten the mixture if necessary.

Divide the batter equally between the prepared tins. Bake in the preheated oven for 20-25 minutes, or until the cakes are golden and spring back to the touch. Remove from the oven and allow to cool in the tins for a 10 minutes before carefully turning out and cooling on a wire rack.

Meanwhile, make the praline buttercream icing. Place the water and sugar in a heavy bottomed saucepan and bring to the boil. While the syrup is heating, place the egg yolk in the bowl of an electric stand mixer fitted with the whisk attachment. When the syrup begins to boil start whisking the yolks at a medium speed. Bring the syrup to the thread stage (115°C/238°F) – a point at which the boiling syrup will have thickened somewhat and when a metal spoon is dipped into the syrup it will fall off in a viscous stream. A definite thread will remain when one of the last drops falls from the spoon.

Pour the hot syrup directly onto the egg yolks in a steady stream, whisking all the time. Take care while adding the syrup, avoid pouring directly onto the moving whisk and aim for the syrup to hit the side of the bowl and let it run down into the yolk mixture below. Whisk the mixture until it thickens and cools to room temperature, approximately 10 minutes.

Beat the unsalted butter into the cooled mousse and finally fold in the 4 tablespoons of powdered praline.

To assemble, remove the baking paper from each cake and split in half horizontally. place one layer of cake on a serving plate and spread with some of the buttercream. Lay the next layer of cake on top and spread with more buttercream. Continue until all four layers of cake are sandwiched together. Cover the top and sides of the cake with the remaining buttercream. Coat the sides and top of the cake with praline powder, you will need to use your hand to press the praline in place, particularly on the sides of the cake, until the cake is completely covered.

Line a baking tray with nonstick baking paper.

Combine the almonds and sugar in a low sided heavy based saucepan and place on a medium heat. After a minute or two the sugar will begin to melt and caramelise. The sugar will not melt evenly so use a wooden spoon to gently nudge the almonds and push them around, as you do the melting sugar will move with the nuts and the contents of the pot will heat more evenly. As the sugar melts and caramelises the almonds begin to roast and you will hear them making a crackling sound. When the caramel is a deep chestnut colour, use a wooden spoon to coat the almonds completely in the hot caramel. Remove the pot from the heat and pour the bubbling mixture directly onto the lined baking sheet. Allow the caramel and nuts to cool completely.

Break the solidified almond brittle into small pieces and pulse to a gritty powder using a food processor. Store in an airtight container.