Rhubarb and custard brioche loaf

Method

1. Mix the flour, yeast, salt and sugar in a large bowl, then make a well in the centre. Heat the milk until lukewarm. Pour into the well, followed by the eggs and vanilla and mix into a smooth, stiff dough. Tip the dough onto a worksurface lightly dusted with flour or into a stand mixer with a dough hook attached. Knead for 5 minutes.
2. Continue to knead the dough, adding the butter in a few cubes at a time, ensuring it’s incorporated before adding more – the dough will be quite sticky but will get easier to work with as you go, so don’t add more flour. This will take about 30 minutes by hand, or 6-8 minutes in a stand mixer on medium speed.
3. Put the dough in a clean bowl and cover with a clean damp tea towel or an unused shower cap (see Eco Tip). Put somewhere warm for 1-2 hours until doubled in size.
4. Once risen, knock the dough back, giving it a light knead. Cover the bowl again and put in the fridge overnight to rest.
5. Meanwhile, heat the oven to 100°C fan/gas ½. Cut half the rhubarb into 1cm slices and the other half into 1cm cubes. Put half the slices in a small saucepan with 10g sugar, 1 tsp water and a pinch of salt, then put over a low-medium heat and simmer gently for about 8 minutes, or until the rhubarb is tender. Tip into a blender, whizz into a smooth purée, then set aside to cool and chill. Reserve the remaining sliced rhubarb for decorating the loaf.
6. Put 50g of the sugar and 50ml water in the same saucepan. Set over a medium heat and bubble gently until the sugar has dissolved. Remove from the heat and stir in the diced rhubarb, ensuring it’s submerged, then set aside for 5 minutes to infuse. Line a baking tray with baking paper, then scoop out the soaked rhubarb and arrange it in a single layer on the tray, leaving as much liquid behind as possible. Bake for 15 minutes until dried out a little, then set aside to cool (with the syrup).
7. Put the milk and vanilla in a pan and heat until steaming (but don’t boil). In a bowl, mix 1 egg yolk with the remaining 50g sugar, cornflour and salt with a wooden spoon. Gradually pour the hot milk mixture over the egg mixture, stirring constantly, until combined.
8. Rinse out the pan then return the custard mixture to it. Cook over a medium heat, stirring constantly, until thickened. It’s ready when it holds its own shape in the pan. Pour into a bowl and cover the surface directly with baking paper. Set aside to cool, then stir in the rhubarb purée and chill.
9. Grease the loaf tin with oil. Remove the brioche dough from the fridge and roll it out into a 40cm square on a lightly dusted work surface. Spread the rhubarb crème patisserie over the dough, then scatter over the lightly dried diced rhubarb. Use a large sharp knife to cut the dough into 4 even strips then layer the strips on top of each other, with the rhubarb side facing upwards. Cut this stack widthways into 4.
10. Tuck the stacks into the loaf tin so they are sitting vertically in a single line. Cover with a damp tea towel or a greased, unused shower cap and set aside in a warm place to prove for 30 minutes, or until puffed up enough that it fills the tin.
11. Heat the oven to 160°C fan/gas 4. Brush the brioche with the remaining egg yolk. Scatter over the remaining sliced rhubarb and 1 tsp sugar. Bake for 50 minutes, covering loosely with foil after 25 minutes to prevent the top getting too dark. Allow to cool in the tin for 10 minutes then turn out onto a cooling rack. Brush the reserved syrup over the brioche as it cools.