Step 1

Preheat the oven to 350 degrees and butter the bottom and sides of a 9-inch springform pan.

Step 2

Gently melt the butter and chocolate together in a bowl over a double boiler, stirring occasionally. You can also melt them in the microwave at half power in 15 second intervals, stirring after each. Let cool slightly.

Step 3

Whisk together the egg yolks and 1/2 cup sugar until light and frothy.

Step 4

Add the melted butter and chocolate mixture, espresso powder, cardamom, vanilla and salt, then whisk to combine.

Step 5

IIn a separate bowl, use an electric mixer or stand mixer to whisk the egg whites and the remaining 3 tablespoons sugar until they form stiff peaks (when they stand straight up and don't collapse), about 3-5 minutes.

Step 6

Use a rubber spatula to gently fold the egg whites into the chocolate mixture, being careful not to let it deflate.

Step 7

Bake for about 40 minutes, or until puffed and no longer jiggly in the middle.

Step 8

Allow to cool completely before cutting.

Step 9

Dust with powdered sugar if desired and serve cold or at room temperature