Choux pastry:

1. Combine the water, milk, butter, salt and sugar in a saucepan and place over low heat until the butter is melted.
2. Once the butter is melted completely, turn the heat on high and bring to a boil.
3. The moment it comes to a boil, remove off heat and immediately add the flour, all at once. Mix well with a wooden spoon or spatula until the flour is well absorbed. Place the saucepan back over medium flame and continue cooking for 2-3 minutes, mixing all the time, until a layer of dough remains on the bottom of the pan – keep the flame on medium to avoid burning and mix all the time with the spatula or spoon to cook out the liquid.
4. Remove from heat and allow the dough to cool down for 10 minutes.
5. Start incorporating the eggs, one by one, mixing well after each addition. Add the last egg bit by bit to make sure you’re not adding too much egg. The number of eggs used depends on the humidity of the dough, even on weather and the size of the eggs.
6. The dough is ready when it falls off the spoon and leaves a streak that doesn’t collapse on itself if you run your finger through it.
7. Spoon the dough into a pastry bag fitter with a round nozzle.
8. Roll the sheet of puff pastry into a thin layer – about 0.5cm thickness.
9. Cut a circle of puff pastry of about 20cm diameter and place it in a baking tray.
10. Pipe a circle of choux pastry on the edge of the puff pastry. Pipe the remaining choux pastry on a different tray into small dollops (choux, profiterols).
11. Bake both the trays in the preheated oven at 350F – 180C for 35-40 minutes or until golden brown, risen and crisp.
12. Allow to cool down.

Vanilla Creme Diplomat:

1. Bloom the gelatin in cold water.
2. Heat the milk in a pot over low heat.
3. In the meantime, mix the egg yolks and sugar, as well as a pinch of salt in a bowl until creamy and pale.
4. Add the cornstarch and mix well.
5. Pour in the hot milk then transfer back on heat and cook for 1-2 minutes until thickened.
6. Remove from heat and add the gelatin.
7. Cover the cream with plastic wrap on the surface and allow to cool down completely.
8. When chilled, mix with an electric mixer until creamy again then add the vanilla and mascarpone and mix well.
9. Fold in the whipped cream then spoon the creme diplomat into a pastry bag fitted with a St. Honore nozzle.

Caramel Creme Diplomat:

1. Bloom the gelatin in cold water for 10 minutes at least.
2. Combine 80g sugar with water in a saucepan and place over medium heat.
3. Cook for a few minutes, washing down the sides of the pot with a brush dipped in cold water, until it begins to turn golden brown and it has a nice amber color.
4. Remove from heat and allow to cool down for 5 minutes. Add the milk and place back on heat.
5. Keep on low heat until the sugar is completely melted.
6. In the meantime, mix the egg yolks with the remaining sugar, plus a pinch of salt. Add the cornstarch and mix well.
7. Pour the hot milk over the cornstarch then return back on heat and cook for 1-2 additional minutes until thickened.
8. Remove from heat, stir in the gelatin and cover with plastic wrap on the surface. Allow to cool down completely.
9. Mix with an electric mixer until creamy.
10. Fold in the whipped cream then spoon half of the cream into a pastry bag fitted with a small nozzle. Reserve the remaining cream aside.

To assemble the gateau:

1. Start by making a tiny hole at the bottom of each choux bun then fill all of them with caramel creme diplomat. Place aside.
2. Make a wet caramel by combining 150g sugar with 65ml water. When it has an amber color, remove from heat and allow to cool down for 1 minute.
3. Take the filled choux buns and dip the top into the hot caramel. Place right away on a sheet of baking paper to set. Work quickly as the caramel tends to cool down and set – if it’s too thick, place it back on low heat for 1-2 minutes then continue dipping the buns.
4. Once the top of each bun is set, reheat your remaining caramel and dip the bottom of the buns as well, glueing them right away on the ring of puff pastry – try to glue them as close to the edge as possible and make sure you use a thin layer of caramel for this step.
5. Once all the choux buns are in place, use the remaining caramel creme diplomat to fill the bottom of the gateau.
6. Top the caramel cream with the vanilla cream, piping it with the special St. Honore nozzle.
7. Decorate with choux buns and caramel strings just before serving.