These flaky, crackly cakes from the Brittany region of France have pockets of caramelized sugar strewn throughout. Martha made this recipe on episode 610 of Martha Bakes.
In a small bowl, combine water and yeast. Stir until yeast dissolves.
In the bowl of an electric mixer fitted with the dough hook, combine flour, salt, and 2 tablespoons melted butter on low speed. Add yeast mixture, and mix until well combined, about 2 minutes.
Cover bowl with plastic wrap, and let rise in a warm place until doubled in size, about 1 hour. Punch dough down, shape into a rectangle, cover in plastic wrap, and place on a baking sheet. Chill for 2 hours in the refrigerator.
Meanwhile, on a nonstick baking mat or parchment paper, roll the remaining pound of butter into an 8-inch square, between 1/8- to 1/4-inch-thick. Wrap in parchment paper, and let rest at cool room temperature, about 30 minutes.
On a lightly floured surface, roll chilled dough into a 12-inch square. Center butter square over the dough so that each side of the butter faces a corner of the dough. Fold the corners of the dough over the butter to enclose. Seal the edges by pinching together. Turn over dough, seam-side down. Roll into a 24-by-8-inch rectangle. Fold dough into thirds, aligning edges carefully and brushing off excess flour. (The object is to ensure that the butter is distributed evenly throughout so that the pastry will puff evenly when baked.) This completes one turn.
Repeat the process of rolling and folding once. Chill for 20 minutes, just until cold but not firm. Then repeat process twice, dusting work surface and dough generously with sugar, about 2 cups sugar total for the 2 turns. You will now have completed 4 turns. Refrigerate dough 20 minutes.
Meanwhile, using a pastry brush, brush 18 (4-by-3/4-inch) ring molds with melted butter. Transfer to 2 baking sheets lined with nonstick baking mats and set aside.
On a sugared surface, roll chilled dough into a 12 1/2-by-24 1/2-inch rectangle, about 1/2-inch-thick. Cut into eighteen 4-inch squares. Fold the corners of one square toward center; repeat process. Lightly press to adhere. Turn square over, and gently coat with sugar. Invert, and place in a prepared ring mold. Repeat with remaining squares. Let dough rise, covered, in a warm place until puffed, 30 to 40 minutes.
Meanwhile, preheat oven to 425 degrees. Bake until golden brown, 25 to 30 minutes. Immediately remove ring molds, and place on a wire rack to cool completely.