FOR CAKE: Preheat oven to 350~. Butter 8" round cake pan with 2" sides. Line bottom of pan with parchment. Stir chopped chocolates in top of doulble boiler over simmering water until melted and smooth. Cool slightly. Process macadamia nuts and flour in processor until nuts are finely ground. Transfer jnut mixture to small bowl. Do not clean processor. Add butter and sugar to processor and blend using on/off turns until mixutre is smooth. Add eggs, Cognac, instant espresso (or coffee) and vanilla and process until smooth. Add melted chocolate and process until just combined. Add nut mixture and process unisng on/off turns until mixture is just combined. Transfer batter to prepared pan. Smooth top with spatula. Bake until toothpick inserted halfway between edge and center of cake comes out clean, about 40 minutes. Cool cake in pan on rack 30 minutes. Invert cake onto rack; remove parchment and cool.
FOR GLAZE: Bring cream to boil in heavy small saucepan. Remove from heat. Add chocolate and stir until melted and smooth. Stir in corn syrup. Let glaze stand until cool enough to spread, about 20 minutes. Transfer cake to rack. Spread glaze over top and sides of cake. Refrigerate until set. Transfer cake to platter. Let stand at room temperature 1 hour before serving.