In a large skillet over medium to low heat, add the peeled hazelnuts and roast them until lightly golden brown.
Remove from the heat, finely chop the roasted hazelnuts and set aside.
Then, cut the puff pastry.
Use the bottom of a removable-bottom cake pan as a guide and cut out a large circle from the pastry using a dough cutter.
Remove the excess pastry and, using a fork, prick the whole pastry.
Add the chopped-up hazelnuts we prepared and press them against the pastry with a rolling pin.
Transfer the pastry to an oven rack and press it between the gaps.
Take to a preheated oven at 180° C (350° F) and bake for 30 minutes.
In a medium saucepan over medium to low heat, add the finely chopped strawberries.
Add the sugar, the lemon and mix everything very well until the strawberry dissolves completely.
Then, dissolve the cornstarch in the water, add it to the jam and keep mixing until it thickens.
Remove from the heat and set aside until it is cool.
In a large bowl, add the whipping cream, the refined sugar and beat everything very well until stiff peaks form.
To assemble the dessert, get a removable-bottom cake pan.
Add the baked pastry, half of the cream and spread it evenly.
Then, add half of the strawberry jam and spread it well.
Add the other half of the cream, spread it and finish by adding the rest of the jam on top of everything.
Take it to the fridge and let it chill for at least 1 hour.
Meanwhile, cut another 300 grams of puff pastry, using the bottom of a removable-bottom cake pan as a guide.
Then cut it into 8 equal triangles, like a pizza, and prick the whole pastry with a fork.
Add the rest of the ground hazelnuts we prepared earlier and press then against the pastry with a rolling pin.
Place it on an oven rack, take it to a preheated oven at 180° C (350° F) and bake for 40 minutes.
After this time has passed, top the dessert with the pastry we baked.
Finish by adding a spoonful of the strawberry jam on top of the dessert.
Serve.