Whisk together the kefir, yeast, sugar or honey and 2 eggs in a stand mixer or large bowl. Tip in the flour along with 1 tsp salt and mix well until there are no pockets of flour. The dough will be a bit wet and shaggy (loose and formless) at this stage. Can be covered and left to chill overnight. Prove for 1 hr in a warm place until puffed up. Knead, using the dough hook attachment of your mixer or with your hands on a lightly dusted surface, for 10 mins until smooth.

Meanwhile, make the filling. Put the poppy seeds, nuts and milk in a small pan over a low heat and simmer, uncovered, for 30-45 mins until all the milk has evaporated. Keep an eye on it so that the milk doesn’t catch. Remove from the heat and leave to cool completely. Will keep chilled in an airtight container for up to three days, or frozen for up to three months.

Transfer the poppy seed mixture to a food processor. Add the butter, both sugars, a pinch of salt and vanilla. Blitz until you have a thick paste.

Line a deep 30 x 20cm baking tray with baking parchment, allowing some overhang. Tip the dough onto a floured surface and knead gently, using floured hands, incorporating the flour from the worktop. The sticky dough will soon begin to feel soft and velvety.

Re-flour the surface generously and, using a rolling pin, roll out the dough into a 40 x 30cm rectangle. You can use your fingers to stretch the edges, if needed. Dot the poppy seed filling all over the surface – it’s fine if there are a few little gaps – gently spreading it with your hands without tearing the dough.

Roll the dough into a log, along one of the longer edges, being careful not to roll it too tightly. Cut the log into 16-18 buns along its length using a sharp knife. Arrange the rolls close to each other on the prepared baking tray. Leave to prove in a warm place for 30 mins until they’re puffed up and nestling into each other.

Heat the oven to 180C/160C fan/gas 4. Brush with the beaten egg mixture and bake for 40 mins, turning halfway through, until golden. If the filling starts to catch, cover with foil. Leave to cool completely in the tray, then tear apart and serve. Will keep frozen for up to a month. Warm in a low oven before serving.