Place the flour in the bowl of a stand mixer; add the yeast to one side and the salt and sugar to the other.
500 g (4 cups + 2 Tablespoons) white bread flour, 7 g (2 ¼ teaspoons) fast action yeast, 1 teaspoon salt, 50 g (¼ cup) granulated sugar
Add in the mashed banana, melted butter and milk and mix on a low speed until it comes together into a dough. Turn up the speed to high and mix until the dough starts to pull away from the sides of the bowl cleanly and is very elastic; it should pass the windowpane test.
250 g (2 medium) very ripe bananas, 50 g (½ stick) vegan butter, 200 ml (¾ cup + 1 Tablespoon) unsweetened soy milk
Transfer the dough to a large, lightly greased bowl, cover with clingfilm and place in the fridge to rise overnight. (Or in a warm place until doubled in size - 1-2 hours).
Line an approx 9.5x5 in loaf tin with baking parchment, leaving some overhanging to make it easier to lift the baked loaf out of the tin. Punch down the risen dough and turn it out onto a lightly floured surface; sprinkle with flour and roll out to a large rectangle, about 30 x45 cm.
Spread the nutella evenly all over the dough, leaving a small border around the edge. roll the dough up tightly from one of the long edges into a log.
300 g (10.5 oz) vegan nutella (or vegan chocolate spread)
Use a sharp knife to slice the log in half lengthwise. Twist the two halves together, tuck the ends under and carefully lift it into the loaf tin.
Loosely cover with oiled clingfilm and set aside to rise until puffy, about 45 mins to 1 hour. Meanwhile, preheat the oven to 190°C/170℃ fan/375°F/gas mark 5.
Bake the risen dough for 60-70 minutes, until the internal temperature reaches at least 94°C/201°F on a probe thermometer. You will probably have to cover the top with tin foil partway through baking to prevent it from catching.
Leave the bread to cool in the tin for 10 minutes then carefully lift it out onto a wire rack and leave to cool before slicing.