Preheat the oven to 350 (F). Prepare a 9-inch springform baking pan by spraying liberally with cooking spray and lining the base with parchment paper. Spray the parchment paper.
In a double boiler (or a heatproof bowl set over a pan of boiling water, ensuring that the bottom of the bowl does not touch the water), combine 1 cup unsalted butter and 8 ounces coarsely chopped dark chocolate. Melt, using a heatproof rubber spatula to stir occasionally. When both the butter and the chocolate are fully melted, remove from heat. Gently whisk in 1/3 cup red wine, and set on a wire rack to cool slightly.
Once the egg and sugar mixture is light and fluffy and has doubled in size, gently fold the cooled chocolate mixture (from the 2nd step) into the egg and sugar mixture until the batter is fully incorporated and is a uniform chocolate color. Transfer the batter to the prepared springform pan and bake for 35 to 40 minutes. Transfer the cake to a wire rack to cool for 10 minutes, before running an offset spatula or butter knife around the cake pan. Remove the side ring of the pan from the cake, and allow to cool on the wire rack.
Serve with fresh whipped cream. As the cake cools, it will deflate and sink slightly — a fresh, warm cake will have a chocolate lava cake texture, while a cool cake will have a dense, brownie-like texture.