Melt butter and chocolate together in the top of a double boiler over simmering water, or in a small heavy saucepan over low heat.
Stir in the sugar and cocoa, then the evaporated milk, extract, and salt.
Continue cooking and stirring until sauce is thickened.
Keep warm while preparing crepes.
Prepare crepes only, substituting 1 teaspoon vanilla extract for lemon peel.
As crepes are cooked, transfer to baking sheets, two or three on each sheet.
Spoon a generous amount of the hot chocolate sauce on one quarter of each crepe, then fold one half of crepe over other half; fold into quarters.
Press surface lightly with a spatula to distribute chocolate sauce to edges of crepe.
Sift confectioners' sugar lightly over each crepe, then quickly place under broiler about 3 inches from source of heat.
Heat about 30 seconds, or until sugar melts slightly.