Peel and mince the onion and garlic.

Heat the oil in a skillet.

Sauté the onion until translucent.

Add the garlic and stir until it releases its aroma.

Add the spinach and cook until it wilts.

Pour 150g of cream over the spinach and simmer until thickened.

Season with salt and pepper and let cool.

Preheat oven to 375°F.

Line a baking sheet with parchment paper.

Dust with flour.

Roll out the dough on the parchment paper. Sprinkle the 1/3 cup of breadcrumbs evenly over the puff pastry.

Mix the cheese with 3/4 cup of breadcrumbs, and the remaining beaten egg with the spinach mixture.

Spread the mixture over the dough, leaving a border around the edges.

Whisk the egg yolk with the remaining cream.

Brush the edges of the dough with this mixture.

Peel the hard-boiled eggs and arrange them in a row on top of the spinach in the upper third of the dough.

Roll up the strudel and seal the ends.

Brush the strudel with the remaining egg/cream mixture.

Bake for 25 minutes.

Transfer to a cooling rack.

Let cool for 15 minutes before slicing and serving.