1 medium-size (6-ounce) baking potato, peeled and quartered
3/4 cup milk
1-3/4 cups (3-1/2 sticks) butter
1/2 teaspoon salt
2 packages active dry yeast
2 tablespoons sugar
2 large eggs
About 4 cups all-purpose flour
EGG GLAZE:
1 large egg
1 tablespoon water
Recipe
1. In a 1-quart saucepan, place the potato and enough water to cover. Heat to boiling over high heat. Cover and cook the potato over low heat until it is fork-tender. Drain the potato and reserve 1/4 cup cooking water. In a small bowl, mash the potato.
2. In the same saucepan, heat the milk until bubbles form around the side of the pan. Remove from the heat and stir in 1/4 cup butter, the mashed potato, and salt. Cool to warm.
3. In a large bowl, place the reserved potato water; cool to warm. Sprinkle the yeast over the water; stir in the sugar, and set aside until foamy, about 10 minutes. Stir in the warm milk mixture and eggs until well combined. Stir in 3 cups flour or enough to make a very soft dough. (The dough should be barely handleable, softer than other bread doughs.)
4. Turn the dough out onto a floured surface. Knead it gently, adding more flour if necessary, just until it forms a soft ball, 1 to 1-1/2 minutes. It should be just barely manageable and will not be elastic. Use a dough scraper to help lift it if necessary.
5. Lightly oil a large bowl. Place the dough in the bowl, turning to bring the oiled side up. Cover it with a clean cloth and let it rise in a warm place, away from drafts, until it is double in size, about 11/2 hours.
6. Meanwhile, cut each of the remaining 3 sticks of butter into 8 pieces and place on a sheet of waxed paper. Sprinkle with 1/3 cup flour. With your fingers, quickly work the flour into the butter just until it is blended in but the butter is still firm. If the butter softens, refrigerate it until it is firm again. Shape the butter mixture into a 6-inch square; wrap it in waxed paper and refrigerate it until it has the consistency of vegetable shortening, about 15 minutes.
7. On a well-floured surface, invert the bowl to remove the dough. Do not punch or manipulate the dough or the croissants will be tough. With a floured rolling pin, roll the dough to a 13-inch square. Unwrap the butter and place it diagonally in the center of the dough. Bring the comers of the dough, one at a time, over the butter to meet in the center, overlapping by I inch. (The sides of the dough will overlap as well to form an envelope.) Press the edges of the dough to flatten and seal in the butter.
8. With the rolling pin, gently roll the dough to an 18- by 9-inch rectangle. Be sure the edges are even. Do not press too firmly or the butter will be forced out. (In a warm kitchen, if the butter softens too much, transfer the dough to a baking sheet and refrigerate it until it is firm.) Bring one 9-inch end of the dough rectangle over the center third of the dough. Brush off the excess flour and bring the other end over the first to form 3 layers of dough.
9. Roll the dough out again to an 18- by 9-inch rectangle. Fold it crosswise in thirds as before, to form 3 layers. Wrap the dough in plastic wrap and transfer it to a baking sheet. Refrigerate the dough 30 to 45 minutes. Repeat the rolling, folding, and rolling process 2 more times, and refrigerate the dough 11/2 to 2 hours the last time.
10. To shape the croissants, cut the dough crosswise in thirds. Work with. one piece at a time; wrap and chill the remainder. Roll the dough out on a lightly floured surface to a 13-inch circle. Cut it into 8 wedges. With your fingers, at the wide end of each wedge, pull the points to widen or stretch the base to about 6 inches. Then gently pull the top point of the wedge to lengthen the triangle to about 7 inches. Starting from the base, roll up the triangle. Place the croissant, top-point underneath so that it won't uncurl, on a jelly-roll or pizza pan. Curve and bring the base points toward the center to form a crescent; press the points together to seal. Shape all the croissants, placing them 2 inches apart on baking pans.
11. Cover the croissants loosely with a clean cloth. Let them rise at room temperature, until the dough feels fight and spongy, I to 11/2 hours. On hot days, refrigerate the croissants intermittently so that the butter is contained.
12. After the croissants have risen, refrigerate them 20 minutes before baking to harden the butter and make them flakier.
13. Heat the oven to 425°F.
Prepare the Egg Glaze:
In a cup, beat together the egg and water. Brush the glaze over the croissants. Bake them 15 minutes. Remove them from the oven; brush each with glaze again; return to the oven; and bake until they are nicely browned, 1 to 2 minutes. Cool the croissants on wire racks 10 minutes, serve warm.
Chocolate Croissants:
Prepare the croissant dough in the basic recipe. On a lightly floured surface, roll one-third of the dough to a 14- by 12-inch rectangle. Cut this into six 7- by 4-inch rectangles. Cut two 3-ounce bars bittersweet or dark chocolate into 6 rectangles, each about 3- by 11/2 inches.
Brush the edges of the dough with egg glaze. Place the chocolate lengthwise along one short end in the middle and roll to enclose the chocolate completely. Press the seam firmly to seal and place the croissant, seam-side down, on a jelly-rofl pan. Cover with a clean cloth; let rise; brush with egg glaze and bake as in the basic recipe.
Blueberry Croissants:
Prepare the croissant dough in the basic recipe. Prepare the blueberry filling: In a 1-quart saucepan, combine 1/4 cup sugar and 2 tablespoons cornstarch; stir in I cup frozen blueberries. Cook over medium-low heat, stirring constantly, until the berries thaw and the mixture bolls. Boil I minute, stirring, until the mixture is very thick. Remove from the heat and stir in 1 teaspoon grated lemon rind. Cover and refrigerate the filling until it is cold and firm, about 2 hours.
Roll one-third of the dough to a 13-inch circle and cut it into 6 wedges. Pull the top point of each wedge to stretch the triangle to about 7-1/2 inches; pull the base points to stretch slightly. Brush the edges of the triangle with the egg glaze. Place one-sixth of the blueberry filling along the base in the middle of triangle. Roll the triangle once to cover the filling; press the dough around the filling to seal completely. Continue to roll the triangle, pulling the top point as you roll to get more turns in the croissant. Place the croissants on a jelly-roll pan, cover with a clean cloth, and let them rise. Brush them with egg glaze and bake as in the basic recipe.