Combine chocolate wafer crumbs and 1/3 cup melted butter; firmly press on bottom and sides of a 9-inch tart pan or pie plate. Bake at 350F for 6 to 8 minutes.
Cream 1/2 cup softened butter; gradually add brown sugar with the electric mixer at medium speed until blended. Add the eggs, one at a time, beating after each addition. Stir in the melted chocolate, instant coffee granules, vanilla extract, flour and chopped pecans. Pour into the prepared crust. Bake at 375F for 25 minutes. Remove from oven and cool completely on a rack.
Before serving, pipe sweetened whipped cream on each piece and drizzle with chocolate syrup. Garnish with cherries and/or mint if desired.