Step 1

Place the heavy cream in the bowl of an electric mixer fitted with the whisk attachment or beaters. Beat on medium speed until soft peaks form. Add the sugar, vanilla, and salt and beat until medium-stiff peaks form. Do not over-whip. (Tip: When whipping cream, keep a close eye on it – it's always done before you think it is, and it goes from perfectly smooth and billowy to grainy and curdled in an instant. Whipped cream should have a smooth, creamy texture and dollops should just barely hold their shape. If you're nervous about over-whipping it, when it's close to done, finish whipping by hand.)

Step 2

Set aside about 1½ cups of the whipped cream. Place about a ½ tablespoon of the remaining whipped cream on each cookie, and stack sideways on a long platter about ¼ inch apart to make one long roll. (The whipped cream is essentially acting as a glue to hold the cookies together.) Spread the reserved whipped cream over the top and sides of the roll. Chill in refrigerator for at least 5 hours or overnight.

Step 3

Using a fine sieve, dust the top of the cake cocoa powder and slice diagonally at a 45-degree angle. Serve with fresh berries, if desired.