• Preheat the oven at 375°F / 190°C. Lightly oil a 25-cm non-stick tart tin.

Prepare the dough.

• In a mixing bowl sift together the flour and baking soda. Set aside.
• In the ball of a standing mixer with the paddle attachment, beat the egg for a minute and add the olive oil. Continue beating and add the yogurt and parmezan. Change to the hook attachment and slowly add the flour. Beat until you have a smooth dough.
• Sprinkle a little flour on a clean working surface and using a rolling pin, roll the dough out until it’s a little bigger than the size of the tart tin. Roll the dough around the rolling pin and carefully unroll it into the tart tin. Gently push the dough onto the sides and trim off any excess with a knife.
• Prick the base of the dough with a fork and cover it with a piece of greaseproof parchment paper. Fill withb eans, lentils or rice and bake for 20 minutes.
• Carefully remove the parchment paper with whatever you used to hold the dough down and avoid rising. You can keep this in a plastic bag for the next tart you bake.

Prepare the filling

• In a wide sauce pan, heat the olive oil and butter in low heat and add garlic, spring onion and leeks. Move them around until they are well coated and let them sauté for 2 minutes.
• Add oregano and thyme, slightly stir and slowly add the vegetable stock or water. Increase heat to medium and let them cook until most of the water has evaporated, for about 10 minutes. Remove from heat and let it cool for 5 minutes.
• Add the feta cheese and gently stir.

Assemble the tart

• Spread the filling evenly inside the tart and sprinkle the grated regato cheese on top.
• Bake for 25-30 minutes.