Step 1

Combine yeast, sugar and half the milk in a bowl. Set aside in a warm, draughtfree place for 10 minutes or until frothy.

Step 2

Combine the flour, extra sugar and salt in a large bowl. Make a well in the centre. Pour in the yeast mixture, butter, sour cream, egg, vanilla, lemon rind and remaining milk. Use a wooden spoon to stir until combined, then use your hands to bring the dough together in the bowl.

Step 3

Turn the dough onto a lightly floured surface. Knead for 10 minutes or until smooth and elastic. Brush a large bowl with oil to grease. Place the dough in the bowl. Cover with a clean tea towel. Set aside in a warm, draught-free place for 11/2 hours or until doubled in size.

Step 4

Meanwhile, to make the filling, place the poppy seeds in a large bowl. Cover with boiling water and set aside for 1 hour to soften. Drain. Place in the bowl of a food processor and process until coarsely chopped. Add the walnuts and sugar, and process until finely chopped. Transfer to a saucepan. Add the raisins, milk, honey, vanilla and butter. Bring to a simmer over medium heat. Cook, stirring occasionally, for 15 minutes. Set aside to cool.

Step 5

Lightly whisk the egg whites in a bowl. Add to the filling and stir to combine.

Step 6

Preheat oven to 180°C. Line a large baking tray with non-stick baking paper. Turn dough onto a lightly floured surface. Roll out to a 30 x 40cm rectangle. Spread filling over dough, leaving a 2cm-wide border. With one short edge facing you, fold the bottom one-third of the dough into the centre. Fold again to enclose. Fold ends under. Place on the lined tray. Bake for 50 minutes or until a skewer inserted into the centre comes out clean. Set aside for 5 minutes to cool before transferring to wire rack to cool completely.

Step 7

Sift the icing sugar into a bowl. Whisk in the lemon juice until the icing reaches pouring consistency. Drizzle over the cake. Set aside for 10 minutes or until set.