(Adapted from Tastemade's Potato Gorgonzola Rosemary Puff Pastry Tart recipe)

Preheat oven to 220°C / 200°C fan.

Line a baking sheet with baking paper and lay puff pastry on top. Using a small sharp knife, score pastry along the edges - 2.5cm from the edge - to create a crust. Prick the base of pastry (inside the crust) with a fork then put it into the fridge while you prepare the toppings.

Slice onion finely and put it into a bowl. Peel the potatoes and slice them thinly using a mandolin. Put them into the bowl and season with sea salt flakes and olive oil. Mix well.

Using your hands, crumble the gorgonzola cheese (or a cheese of your choice) until fine. Place gorgonzola cheese, mascarpone cheese & heavy cream into a bowl and mix well.

Bring pastry out of the fridge and spread cheese filling evenly over the pastry (inside the crust). Place potato and onion slices over the cheese filling neatly so that they slightly overlap.

Grind black pepper and add fresh rosemary on top of the tart, then brush egg yolk over the crust. Place tart in oven and bake for 25-30 minutes, until the pastry has browned and potatoes are starting to curl up. Do keep an eye on the pastry to ensure it doesn't become too brown. Once cooked, remove from oven and serve.