1. Preheat the oven to 350°F. Butter and flour an 8-inch springform pan.

2. Place a large heatproof bowl over a pot of simmering water, making sure the water doesn't touch the bowl. Put the butter and chocolate in the bowl, stirring occasionally, until the chocolate melts. Take the bowl off the heat; set aside.

3. Whisk the sugar into chocolate mixture, then whisk in eggs, coffee, and salt until combined and smooth. Sprinkle on the 1/4 cup flour and fold it in with a rubber spatula until flour is incorporated.

4. Pour batter into the prepared pan; place it on a sheet pan. Bake 30 to 40 minutes, until the top puffs and cracks and cake doesn't wobble when you jiggle the pan. Cool completely on a wire rack. (The cake will deflate as it cools.) Run a small knife around edge of cake and remove sides of springform pan. Cut cake into wedges and serve warm or at room temperature with Sweetened Whipped Cream. If desired, garnish with additional chocolate. Serves 8.

Sweetened Whipped Cream

1. Pour 1 cup cold heavy cream into the bowl of an electric mixer fitted with the whisk attachment. Add 1 tablespoon sugar and 1 teaspoon pure vanilla extract and beat on high until the cream forms soft peaks. Makes 2 cups.

Tips

The baking time of this cake is sensitive to the pan size and no two 8-inch pans are exactly the same. Start checking the cake after 25 minutes.