1) To make the cookies: Beat together the butter, sugar, cocoa, salt, and flavorings for several minute, until well combined. Scrape the sides and bottom of the bowl.
2) Add the egg and beat for about 5 minutes, until the mixture is fluffy.
3) Stir in the flour and nuts.
4) Cover the dough, and refrigerate for 30 minutes. Towards the end of the chilling time, preheat the oven to 375°F.
5) Press 1 teaspoonful of chilled dough into the bottom and up the sides of each mold. Place the molds, dough side up, on a baking sheet.
6) Bake the cookies for 10 to 12 minutes, until they appear set. Cool for a few minutes, then push on the wider edge of each cookie to pop it out of the mold.
7) While the cookies are cooling, make the filling. Heat the cream until steaming; a microwave works well here. Add the chocolate, stirring until it melts. Reheat briefly on low heat if the chocolate doesn't completely melt. Cool until the mixture thickens somewhat, whisking often.
8) Spread a bit of the chocolate on the flat side of half the cookies. Let them sit for a few minutes to partially set up, then top filled cookies with unfilled cookies, to make sandwiches.
Yield: 5 dozen cookies.