01 -
Heat oven to 450°F. Grease two 6-ounce ramekins and place on baking sheet.
02 -
Microwave butter and chocolate in 20-second intervals, stirring between each, until smooth. Stir in espresso powder.
03 -
Whisk both sugars into chocolate mixture. Add egg, yolk, and vanilla, mixing well.
04 -
Gently mix in flour and salt just until combined. Don't overmix.
05 -
Divide batter between ramekins. Bake 11-12 minutes until edges are firm but center jiggles slightly.
06 -
Cool exactly 1 minute. Carefully invert onto plates and serve immediately.