Custard cream: Place the milk, sour cream, 35g of the sugar and vanilla bean paste into a pan. Add the lemon and orange peel. Slowly heat, continually stirring to avoid curdling, until reaches boiling point. Turn off the heat and set aside. If it is heated too fast it will curdle but it can be brought back by whisking vigorously. After 10 minutes remove the fruit peel.

Mix the egg yolks with the remaining 30g of sugar until paler and increased in volume. Add the cornflour and mix until it is fully dissolved. Return the milk to the heat and when it starts to boil add the egg/sugar mixture. Turn the heat down and cook for 5 minutes until it cooks out the cornflour and thickens. Gradually add the butter and whisk until incorporated. Cover the mix with clingfilm and set aside.

In the large bowl with the flour, make a well in the centre and add the beaten egg gradually until it is incorporated. Add the butter piece by piece until it starts to come together then mix by hand. Form into a ball then cover with a cloth and leave in a warm place for 1 – 2 hours until it has doubled in size. Place it on a floured surface, roll it flat using a rolling pin until it is thin. Cut the dough into tall triangles or long rectangles around 15 cm x 9 cm.

Place a dollop of the custard cream on each bottom and roll up as one would a croissant. Place on a baking sheet covered with baking parchment and leave to rest for 30 minutes. Heat neutral oil such as sunflower in a large pan until it reaches 180 degrees C. Add the doughnuts in batches and turn frequently for an even cook. They should be golden in colour. Remove from the pan and place on kitchen paper to absorb any excess oil.

Roll in sugar or cinnamon sugar.