Preheat oven to 475 degrees. Grease two 6 ounce ramekins with butter and set aside.
Place the chocolate in a microwave-safe bowl. Microwave on high at 30 minute intervals, stirring it between each interval until it's completely melted.
In a separate bowl, beat the butter and sugar using an electric mixer until light and creamy. Add the eggs and mix until well combined. Add flour, coffee and salt. Mix to just until combined.
Fold half of the chocolate into the batter. Add the rest of the chocolate and gently fold to combine.
Divide the batter evenly between the two ramekins.
Bake only until the tops have set and the edges begin to separate from the ramekins, about 11-12 minutes. Remove from the oven and let it sit for about 5 minutes.
Flip each ramekin upside down into a small plate. Dust with powder sugar and top with a scoop of raspberry sorbet.