Chocolate Espresso Cake

FOR THE CAKE:
Preheat oven to 350 degrees F.

Butter and flour 9-inch diameter nonstick cake pan. Melt chocolate and butter in heavy medium saucepan over low heat, stirring constantly until smooth. (Do not burn.) Stir rum and espresso powder in large bowl until espresso dissolves. Whisk sugar and eggs into espresso mixture to blend. Whisk in vanilla and salt. Stir in warm melted chocolate mixture, then flour. Transfer batter to prepared pan. Bake until cake just puffs in center, about 45 minutes. Cool in pan on rack, 15 minutes. Cake will deflate as it cools; guide edges into pan as it cools. Run small sharp knife around edges of cake. Turn cake out onto rack and cool completely.

FOR THE GLAZE:
Stir rum and espresso powder in small bowl until espresso dissolves. Bring cream and butter to boil in heavy small saucepan. Remove from heat, add chocolate and stir until smooth. Stir in rum mixture and corn syrup. Let glaze stand at room temperature until no longer hot, but still liquid.

Place cake on 8-inch cardboard cake round. Set cake on rack over baking pan. Gradually pour glaze over cake, covering completely. Chill until glaze is set. Cake can be made 2 days ahead. Keep cake refrigerated.