On a well floured surface and rolling pin, roll out the puff pastry to fit into an 11 inch tart pan with a removable bottom.

Ease the pastry into the tart pan, ensuring that it goes up the sides all the way. Any excess can be gently folded down into the tart.

Prick the bottom of the shell with a fork.

Lay a piece of parchment over the pastry (I take a square a couple of inches larger than the tart pan and fold it in half, then in quarters, then in eighths, till a tight triangle is formed. Trim across the top evenly. Open it up and it should roughly resemble a circle) Once the parchment is on the tart and gently eased into the edges, fill with pie weights or dry beans etc.

Preheat oven to 350F. Place the tart shell in fridge for 20 minutes.

Place tart shell on a large baking sheet and put into the middle of the warmed oven. Bake this way for 20 minutes.

Remove from oven, gently remove parchment and beans.

Return to the oven for another 5 to 10 minutes or until just turning golden. Watch to ensure that no air bubbles arise, if they do, gently use a tea towel to push them back down. Or else use a fork to create small holes to release the air and push gently down.

Remove from the oven and set aside. Don't turn off the oven.

FILLING

Warm a cast iron skillet over med heat. Add the walnuts and toast for about 5 minutes. Watch to make sure they aren't burning. You want them fragrant and toasty, but no more than that.

Remove from the pan and place on a cutting board to cool. Rough chop them.

In the same skillet heat about 2 tbsp olive oil over med high heat. Add the onions and cook for about 5 minutes. Then add the garlic. Continue cooking until softened and starting to turn golden brown. Adjust the heat if necessary.

Season with salt and pepper (about 1 tsp of each) and add the rosemary and chilli flakes. Stir.

Add the ricotta, walnuts and crumbled gorgonzola and gently fold to combine. Let the filling cool slightly in the pan.

Place the filling into the waiting tart shell.

Increase the oven temperature to 400F.

Peel the potatoes. Using a mandolin, slice the potatoes thinly until you have enough to cover the tart in concentric circles. I'm thinking about 1 1/2 to 2 cups.

Lay out the potatoes over the filling, overlapping in a pattern that pleases you.

Drizzle about 2 tbsp or so of olive oil over the potatoes. Don't drown them, but ensure that they are evenly coated. This will help in browning them.

Toss the 1/2 cup of parmesan evenly over the potatoes. Scatter the remaining rosemary leaves over the parmesan.

Place the tart pan on the baking sheet back into the oven and bake for 20 minutes or until the potatoes are golden brown and the edges are crisping up.

This can be served warm or at room temperature.