Make the sponge:Mix the sponge ingredients well and allow the sponge to stand, covered and in a warm place, for 3 hours or until it has expanded to 2 cups.
Start chilling the butter:Dust one sheet of the paper with 1 tablespoon of flour. Slice the butter into pieces 1/4 inch thick, placing them closely next to each other to form a square. Dust with the second tablespoon of flour.
Place the second sheet of paper on top of the butter and roll it, forcing the butter into a rectangle about 9″ x 9″ (23 cm x 23 cm). Put the butter, between its two sheets, in the fridge for 1 hour.
It’s a good idea to follow the dimensions suggested in this recipe, to make 12 even-sized croissants. I actually took a steel ruler and measured everything as I went along.
Make the dough:Into the starter, mix the dough ingredients.
Knead on a floured surface, adding up to 3/4 cup more flour to get a light, kneadable dough. The original recipe says up to 1/4 cup more flour, but either that’s a typo or the quality of my Israeli flour is very different, because it took 3/4 cup added flour to get a dough that stayed together.
Cover the dough and chill it in the fridge for 1/2 hour.
Roll the dough and butter together:Flour your working surface heavily. Keep extra flour handy for rolling at all times from now on.
Place the cold dough on your floured surface and roll it out into a 15″ x 10″ (38 cm x 25.4 cm) rectangle.
Use the edge of your ruler, or your hand, to push the dough into the desired dimensions with straight edges. It makes a difference, when you cut the dough into triangles later.
Cut the butter in half. Put one half of the butter across the center one-third of the dough.
Fold one end of the dough over the butter. Place the other half of butter on top of it.
Fold the last third of the dough over the butter. This makes a package of dough-butter-dough-butter-dough. It should be about 10″ x 5″ (25.4 cm x 12.7 cm). Pinch the edges together so that no butter shows. If the dough tears, exposing the butter, pinch a tiny piece off the dough and smooth it on over the tear.
Roll out the dough into a rectangle 10″ x 5″ (25.4 cm x 38 cm). Chill it in the fridge for at least an hour.
After the hour, repeat the last step, not adding any more butter, just rolling it out to 10" x 15" (25.4 cm x 38 cm), folding into thirds, rolling it out and folding again. Chill the dough another hour. Or, as I did, wrap the dough up in plastic wrap and let it rest overnight in the fridge.
Shape the croissants:Line two shallow baking pans with baking paper and grease the paper lightly by rubbing a stick of butter over it.
Flour your work surface again and cut the dough into six 5″ x 5″ (12.7 cm x 12.7 cm) squares. Cut each square diagonally to make 12 triangles 5″ x 5″ x 7″ (12.7 cm x 12.7 cm x 18 cm). Roll each triangle out to 1/8″ (about 1 cm) thickness, staring from the longest side to the point.
Starting at the longest side, roll it up tightly. Turn it so that the point is underneath the roll. Bend both ends to make them curl toward the middle, making a crescent. Place the croissants on the baking pans and let them rise in a warm place for 1 hour.
Bake:Glaze the croissants with an egg beaten with 1 tablespoon milk and 1 tablespoon sugar.
Preheat the oven to 375° F (190° C). Bake the croissants for 20 minutes, then turn the oven off and let them sit in there for another 10 minutes before removing them. They should be golden-brown, with a gently crisp crust and a tender crumb.
Fetch the jam, Ma, I’m going to eat.
Sourdough Croissants Recipe from Unpacked – https://jewishunpacked.com/sourdough-croissants/