Silverbeet and mushroom calzone

Pizza dough

• 30 g olive oil, plus extra for greasing
• 220 g warm water
• 1 tsp sugar
• 2 tsp dried instant yeast
• 400 g baker's flour, plus extra for dusting
• 1 tsp salt

Spinach filling

• 100 g mozzarella cheese, cut into pieces (2-3 cm)
• 50 g Parmesan cheese, crust removed and cut into pieces (1-2 cm)
• 50 g feta cheese (firm), cut into pieces (1-2cm)
• 50 g roasted red capsicums, cut into pieces
• 20 g pitted black olives, cut into slices
• 3 sprigs fresh basil, leaves only
• 20 g olive oil
• 2 garlic cloves
• 1 brown onion, cut into halves
• 300 g fresh silverbeet (approx. 2 bunches), trimmed and cut into pieces
• 100 g fresh Swiss brown mushrooms, cut into quarters
• 1 tsp salt
• ½ tsp fresh ground black pepper