Brioche buns with cheese

Brioche buns

• 220 g full cream milk
• 40 g fresh yeast, or 3 tsp dried instant yeast
• 100 g white sugar
• 500 g plain flour, plus extra for dusting
• 80 g salted butter, softened
• 1 egg
• 1 egg yolk (reserve egg white for filling)
• ½ tsp sea salt

Cheese filling

• 1 egg
• 80 g white sugar
• 1 tsp vanilla sugar
• 500 g fresh ricotta cheese, well-drained, or quark
• 100 g sour cream
• 1 egg white, lightly beaten