1.Preheat oven to 400 degrees. Grease the inside bottom and sides of two 5-ounce ramekins with butter. Place 1 teaspoon granulated sugar in one ramekin then shake the sugar around so it sticks to the butter on the bottom and sides of the ramekin. Shake out any remaining sugar into the second ramekin. Do the same with the second ramekin then shake out remaining sugar.
2.Place chocolate and 2 1/2 tablespoons butter together in a bowl and melt in the microwave for 30 seconds at 50% power. Stir and heat an additional 15 seconds if needed. Stir until smooth.
3.In a medium mixing bowl, beat the egg, yolk, sugar, vanilla, and salt together until pale in color. Mix in the melted chocolate/butter. Add the flour and mix until just combined.
4.Pour batter evenly into both the ramekins and then place in the oven directly on the middle rack and bake for 11-12 minutes until top is set but cake still jiggles in the middle.
5.Let the cake sit for 1-2 minutes. Run a sharp knife along the sides of the cake to ensure it comes out perfectly. Invert the cake onto a plate by placing a plate upside down on top of the cake. Flip the cake so that the plate is on the bottom and cake is upside down on top. Leave it for 20 seconds, give the bottom of the ramekin a couple of pats and then lift it straight up.
6.Dust the cakes with powdered sugar and garnish with berries and serve with ice cream.