Ingredients for the dough:
500g cake flour or half-half white and wholemeal cake flour or spelt flour
20g fresh yeast or 2 tsp dried fast action yeast
250 g butter or margarine (the best is half-half and my mum's secret ingredient is 100g butter, 100g margarine and 50g lard)
50 g sugar, icing sugar is best, but others will do too
2 medium eggs (or large or small but then the quantity of the milk will be different)
100 ml milk
a pinch of salt ( there is a pinch of salt in everything in Hungarian cooking)
Traditional method. Dissolve the fresh yeast in 50 ml of milk sweetened with a tsp sugar. if using dry yeast, mix it with the flour. Rub the fat with the flour until crumbly, using your cold fingertips. Add the sugar and the yeasty milk if using. Add the eggs and knead all together to an elastic, not sticky but not hard dough. If is too dry, add milk by spoonfuls. If is too wet, add more flour. All this can be done in a mixer.
My lazy but fast method. Put everything in the food processor, mix it until it all comes nicely together, usually a minute or two.
Very important to work this dough in the cold. The fats shouldn't melt (from the long work in the heated kitchen with warm hands) or the result will be "bacony", heavy chewy. Beigli dough should be light, crumbly but not falling apart dry. So speed and temperature are important.
The dough now needs a rest in a cold place, covered in plastic wrap. As is winter, I put it in the cold garage, the fridge is usually too full.
After a minimum 2 hours or overnight rest (it will stay happy in the cold for a couple of days) divide the dough for 4/6/8 pieces, depending how big you want them to be. Roll out each piece to a rectangle of 2mm thick (or as thin you can). Spread the appropriate amount of filling (usually the weight of the dough must be the same as the weight of the filling, the best is to use an electric scale but I'm sure my Grans in the last century did have wonderful results without one), roll it up starting from the longer edge, making sure the ends are tucked in so the filling won't leak out. Pack the rolls neatly together on a greased and floured baking sheet with edges (or line the sheet with baking parchment) and brush the tops of the rolls with an eggwash. Traditionalists use yolks only but it works perfectly with whole eggs too. for the marbled effect on the picture do the first brushing in only one direction (say lengthwise).
Cover the rolls with another baking sheet (or clingfilm but that might attach to them ruining the marbling) and put the tray in somewhere cold like the garage. Or if you have a large fridge with space, put it there for at least half hour.
After the rest bring the rolls back in the kitchen, brush them with the eggwash in the other direction and leave them rest again in cold for half hour.