Ingredients

  • 3 tablespoons granulated sugar
  • 3 tablespoons packed light brown sugar
  • 1/2 teaspoon freshly ground cinnamon (half of a 3-inch stick)
  • 1/2 recipe croissant dough (1 lb 6 oz), chilled
  • 1 large egg, beaten
  • 1/4 cup unbleached all-purpose flour
  • 1/4 cup granulated sugar
  • 1/2 stick (1/4 cup) frozen unsalted butter, cut into 1/2-inch pieces
  • Special equipment: parchment paper, a ruler, a pastry brush, a garbage bag (unscented)

Method

  • Butter a 24-centimeter (about 9-inch) springform pan and line with a round of parchment paper.
  • Butter paper and remove side of pan.
  • Stir together sugars and cinnamon.
  • Roll out dough on a lightly floured surface, dusting with flour as necessary, into a 24- by 9-inch rectangle.
  • Brush off excess flour with pastry brush and trim edges with a pizza wheel or sharp knife.
  • Arrange dough so that a long side is nearest you and sprinkle cinnamon sugar over dough, leaving a 1-inch border along bottom edge.
  • Brush border with some beaten egg and chill remaining egg.
  • Fold top edge of dough over about 1 inch.
  • Using both hands, roll dough toward you: Use your thumbs to tuck dough under and tighten as you go, working your way down entire length of log (as when rolling up a poster), and gently rock dough back and forth to keep it taut and even.
  • When finished, roll log back and forth over seam to seal.
  • Transfer log, seam side down, to bottom of springform pan, bringing both ends of log together to make a ring.
  • Beginning 2 inches from where ends meet, make vertical cuts from outside of ring toward center at 2-inch intervals, cutting halfway through ring.
  • Attach side of pan and slide pan into garbage bag, propping up top of bag with inverted glasses to keep it from touching dough, then tuck open end under pan.
  • Let ring rise until slightly puffy and spongy to the touch, about 2 1/2 hours.
  • Blend flour and sugar in a food processor.
  • Add frozen butter and pulse until very finely chopped.
  • Chill streusel until ready to use.
  • Preheat oven to 375F.
  • Gently brush top and center of ring with some of remaining beaten egg, then sprinkle with streusel.
  • Bake in middle of oven until top is browned and streusel is crisp, about 45 minutes.
  • Cool in pan on a rack 10 minutes, then run a thin knife around edge to loosen and remove side of pan.