Add a pinch of sugar and a pinch of flour to 50 g of lukewarm water and mix in 1 tea spoon of yeast. Set aside for 5-10 minutes.
Mix warmed to softness butter (50 g) with sugar and eggs (save 1 egg yolk for later use), gradually adding flour.
Next add water with yeast, mix, add more flour. Turn out soft dough onto a floured surface and kneed briefly until smooth.
Transfer the dough to a lightly buttered bowl.
Cover with plastic wrap and let rise until doubled in bulk, about 45 minutes.
Punch down, let rest briefly before rolling out.

To make the filling, cut in very cold butter using a knife until all flour is blended in tiny pieces.
Mix in sugar and vanilla. Set aside.

Preheat oven to 350 degrees F.

Place dough ball on a lightly floured board and roll it out using a rolling pin in a round.
Place the buttery filling on one side of the dough. Next fold the dough over and crimp the edges.
Carefully transfer it upside down into oiled round baking form (10 in)
Make the surface even, brush the top of with egg-yolk glaze (beaten egg yolk and a pinch of sugar).
Bake for 30-40 minutes in the preheated oven, until it's nicely golden brown all over.