Line a 7-inch round cake pan with parchment, then spray with non-stick cooking spray; set aside.

Melt the butter & chocolate chips over a double boiler or in 30-second bursts in the microwave, stirring until smooth.

While the chocolate is still hot, stir in the espresso powder, sugar (if using), and salt until dissolved. Set aside to cool slightly.

In a separate bowl, or in the bowl of a stand mixer, place whole eggs.

Whip on a medium-high speed for 4-5 minutes, or until the eggs are pale and tripled in volume.

Fold the whipped eggs into the chocolate mixture in 3 batches, being sure to fold slowly and thoroughly between each addition.

Do not overmix, as doing so will cause the air in the eggs to deflate the batter.

Pour the batter into your prepared pan.

OVEN DIRECTIONS:

Preheat the oven to 300 degrees F. Securely wrap the bottom of your cake pan in 2 layers of aluminum foil to prevent water from seeping inside the pan.

Set the cake pan into a larger (9-10-inch) cake pan. Fill the larger pan with boiling water until it reaches halfway up the sides of the cake pan.

Bake for 30-40 minutes, or until the cake has risen slightly and the edges are beginning to set (the center will still look slightly wet).

Remove the cake from the water bath and allow it to cool completely on a wire rack before removing it from the pan and serving.

Dust cooled cake with sweetened cocoa powder and garnish with fresh raspberries.

INSTANT POT DIRECTIONS:

Cover the cake pan with a piece of aluminum foil, pressing the foil on the top of the batter to keep it from sweating.

Set the cake pan on a foil sling. Pour ½ cup of water in your Instant Pot or electric pressure cooker, then set a trivet or egg rack inside.

Using the sling, gently lower the cake onto the trivet.

Secure and seal the lid; cook on Manual High Pressure for 35 minutes.

Allow a full Natural Release (about 8-10 minutes) before carefully removing the cake.

Let cake cool completely on a wire rack before removing it from the pan and serving.

Dust cooled cake with sweetened cocoa powder and garnish with fresh raspberries.