Sprinkle yeast over lukewarm water to dissolve.
Scald milk, remove from heat, and cool to lukewarm.
Combine milk, yeast, and l 1/2 cups of the flour and beat vigorously until smooth.
Cover with a tea towel and let stand in a warm place, away from drafts, until light or until mixture has big dimples on the surface.
Now add 4 tablespoons of melted butter, 4 tablespoons sugar, egg yolks, salt, grated lemon, and the remaining 3 cups of flour.
Knead the mixture, right in the bowl, until smooth and springy.
Cover with a tea towel and let rise in a warm place until double in size this takes several hours.
Transfer dough to a floured board and roll about 3/4 inch thick in a long rectangular shape (dough is elastic and springs back, but persevere).
Brush the surface with 2 tablespoons of melted butter and sprinkle with remaining 2 tablespoons of sugar, the cinnamon, and currants.
Roll tightly and cut in 1 inch slices.
Work brown sugar with remaining butter, spreading it over the bottom of a heavy skillet.
Place the swirls of dough on top of sugar mixture, spacing them evenly, and let rise again, in a warm place, until double in size.
Bake in a preheated 350° oven for 30 minutes or until well browned on top.
Invert skillet over cooling rack.