Leek and ham tart

Pastry

• 100 g unsalted butter plus extra for greasing
• 200 g baker's flour plus extra for dusting
• 100 g ricotta well drained (see Tips)
• 1 tsp baking powder
• 1 tsp salt

Filling

• 200 g Gouda cheese cut into pieces (3 cm)
• 350 g leeks trimmed and cut into rings (approx. 5 mm)
• 400 g water
• 150 g pouring (whipping) cream
• 4 eggs
• 100 g ham cut into pieces (2 cm), (see Tips)
• ¼ tsp ground black pepper
• ½ tsp salt
• 1 pinch ground nutmeg