For the Dough

• 6g/2 tsp osmotolerant dried yeast
• 70g/2½oz/¼ cup plus 2 tsp tepid water
• 280g/10oz/2 cups white bread flour
• 70g/2½ oz beaten egg (about 1½ eggs)
• 45g/1½oz/3 tbsp butter, cut into cubes
• 5g/1 tsp fine/table salt
• 25g/1oz/scant 2 tbsp caster/superfine sugar

For the Filling

• 125g/4½oz/½ cup passionfruit juice, fresh or frozen
• 125g/4½oz/scant ¾ cup caster/superfine sugar
• 2 large eggs plus 40g/1¼ oz beaten egg yolk (about 2 yolks)
• pinch of salt
• 125g/4½oz/9 tbsp unsalted butter, softened
• 140g/5oz/⅔ cup double/heavy cream

• vegetable oil, for deep-frying
• granulated sugar, for dusting

1. Dissolve the yeast in the water. Add the flour and egg and mix well, then knead the dough until smooth and stretchy. Work the butter and salt in until thoroughly combined and the dough is silky again, then add the sugar and knead for a few more minutes until the dough no longer feels sticky or gritty. Cover the dough and leave to rise slowly in the refrigerator for 12–14 hours (typically overnight).
2. Grease a piece of baking parchment. Divide the dough into 10 equal-size pieces, shape them into small balls and place them seam-side down on the baking parchment, 5cm/2in apart. Cover and leave to rise at room temperature for 3–3½ hours until doubled in size.
3. Place a heat-resistant bowl over a saucepan half-filled with boiling water, so the water is not touching the bowl and adjust the heat so that the water continues to barely simmer. Put all the filling ingredients except the butter and cream into the bowl and stir constantly until the mixture is thick enough to coat the back of a spoon. Remove the bowl from the pan and stir in the butter until melted. Place this mixture in a clean container, cover the surface with clingfilm/plastic wrap to prevent a skin forming and leave to cool and set at room temperature, then whip it with the cream until thickened.
4. In a deep, heavy pan, heat the vegetable oil to 180–190°C/350–375°F. Lower several dough balls into the oil and fry for about 2 minutes on each side. Remove with a slotted metal spoon, drain off the excess oil, then roll them in the granulated sugar and leave to cool on a wire cooling rack while you fry the remaining balls of dough.
5. Push a small, serrated knife into the side of a doughnut and cut an upside-down “V” shape. Place the filling in a piping/pastry bag with a plain nozzle/tip, push it well into the cut and fill the doughnut until it starts to expand slightly. Repeat to fill the remaining doughnuts.