Chocolate Caramel volcano cake

INGREDIENTS
CHOCOLATE CARAMEL:

5 ounces semi-sweet chocolate
1 cup sugar
2 tablespoons water
1/2 cup whipping cream, at room temperature
2 tablespoons butter, but into small pieces
1 teaspoon good quality sea salt (Maldon/fleur de sel)
LAVA CAKE:
Butter and cocoa powder, for dusting ramekins
½ cup butter
10 ounces semi-sweet or unsweetened chocolate
3 eggs, large
3 egg yolks
1/2 cup flour
1/2 cup powdered sugar
1 teaspoon sea salt
2 tablespoons black cocoa powder (optional)
Maldon sea salt
Powdered sugar for dusting

TO MAKE CHOCOLATE CARAMEL:

Melt chocolate in a double boiler or metal bowl over a pot of simmering water
Add sugar and water to a large pot (make sure it is large, it will bubble up lots)
Heat mixture over medium-high heat until it is dark amber in color and reaches 350 degrees. Remove from heat.
All at once add the whipping cream. Be very careful as it will steam and bubble ferociously. Whisk the mixture until the bubbling stops and the mixture is smooth. Add the chocolate and whisk till combined. Stir in butter.


TO MAKE THE CAKE:

Liberally brush butter to thoroughly coat 4 ramekins. Dusk each with cocoa powder and tap upside down to remove excess. Set aside
Melt the butter and chocolate in a double boiler or a metal bowl over a pot of simmering water.
Whisk the eggs and egg yolks together in a large bowl.
In a medium-sized bowl whisk together the flour, powdered sugar, salt and optional black cocoa powder.
When chocolate has melted (allow it to cool for several minutes if it is hot) add it to the eggs and stir well. Then add the whisked flour mixture to the egg and chocolate and mix until smooth.
Fill each ramekin halfway. Then, place a small tablespoon of caramel on top and sprinkle with salt. Cover with cake batter until 1/2 inch from the top of the ramekin.
Preheat oven to 420 degrees. Bake for 15-20 minutes. Remove from oven and run a knife along the edges of the cake to loosen. Hold a plate over the top of each ramekin. Using oven mitts, turn the plate and ramekin over together so that the ramekin is inverted on the plate. Carefully remove the ramekin. Repeat with remaining ramekins and dust with icing sugar.