Lift the parchment to remove the cake from the pan, which should be cool, and set it on a flat work surface, with a long side facing you. Using a fine-meshed sieve, lightly dust the top with cocoa powder, then spread all of the whipped cream over the cake evenly, covering the entire surface.
Lift up the near edge of the cake and parchment, fold it away from you about 2 or 3 inches over the whipped cream, and begin to peel the paper off the cake. Roll the cake another few inches, pressing against the parchment to make a tight spiral and then gently peeling it off as the cake layer rolls away from you. Complete the roll, keeping it just on the far edge of the parchment sheet. Cover the roll by tucking the loose parchment around and underneath so that the cylinder is well wrapped and can be moved easily. The roulade can now be refrigerated in the paper for 3 or 4 hours or transferred immediately to a platter for serving.
Serving the cake
When ready to serve, transfer the roulade to the serving platter. Remove the parchment paper, gently rolling the cake into the center of the platter, with the seam on the bottom. (If the roll has slumped or twisted, lay a piece of plastic wrap over the top and sides and reshape with your hands.)
With a sharp knife, trim both ends of the roll with neat crosswise or diagonal cuts. Dust the top of the roulade with cocoa and powdered sugar, and garnish with strawberries.
To serve, cut the roll into one-inch thick slices and lay them flat on dessert plates. Top with additional crème chantilly if you like.
This recipe appears in "Julia and Jacques Cooking at Home," published by Alfred A. Knopf, 1999