Artichoke Tart - Torta di carciofi

Pastry

• 100 g Parmesan cheese, cut in pieces (2 cm)
  of vegetarian hard cheese, cut in pieces (2 cm)
• 200 g plain flour, plus extra for dusting
• 1 pinch fine sea salt
• 100 g unsalted butter, cold, diced
• 50 g milk
• 1 egg white, lightly beaten

Filling

• 100 g onions, quartered
• 2 garlic cloves
• 30 g unsalted butter, diced
• 100 g frozen spinach, defrosted, drained
• 2 medium eggs
• 2 egg yolks, from medium eggs
• 250 g double cream
• 1 tsp fine sea salt
• 1 pinch ground black pepper
• 100 g large black olives, pitted
• 480 g tinned artichoke hearts, large, drained, halved (drained weight)