1. Combine water, granulated sugar, corn syrup, toasted hazelnuts, almonds, and salt in a saucepan. Cook on medium-high until golden, about 3 minutes. Add bicarb soda, stir well, spread on an oiled tray, and set.
2. Break praline into pieces, process into a smooth paste, and set aside.
3. Mix flour, caster sugar, and salt in a bowl. Add egg yolks, forming a paste.
4. Gradually whisk in hot milk. Cook mixture over medium heat until thickened, about 5 minutes. Add vanilla and cold butter, mix until smooth. Sieve, chill for 3 hours.
5. Add praline paste to chilled cream, mix. Beat softened butter, add cream gradually, and pipe.
6. Preheat oven to 325°F. Line a tray with baking paper.
7. Boil water, butter, salt, and sugar. Add flour, stir to form dough, cook on heat for 4 minutes. Cool for 10 minutes.
8. Incorporate eggs one at a time. Pipe dough into rings, brush with egg wash, sprinkle almonds, and bake for 35-40 minutes.
9. Cool, slice, fill with cream, and dust with powdered sugar.