Thaw the puff pastry. Then place the puff pastry sheets on top of each other and roll them out into a rectangle.
Blanch the spinach and drain on kitchen paper. Spread the spinach on the puff pastry and season with salt and pepper.
Whisk the cream cheese with an egg yolk and distribute the mixture over the spinach. Place the fish fillets in the middle and roll everything up into a strudel.
Brush the surface with egg yolk and bake everything for 30 minutes at 220 ° C (electric stove) on a sheet lined with aluminum foil. Dice the tomatoes and fry them in a little oil.
Add the chopped garlic. Season with salt, pepper and thyme and serve with the strudel.