6 ounces chopped bittersweet chocolate (at least 70% cacao )
½ cup unsalted butter (room temp) plus some for buttering the pan
Preheat the oven to 350º F.
Lightly butter the bottom and sides of a 9-inch springform pan and then line it with parchment paper. Set aside.
Bring a few inches of water to a boil in the bottom half of a double boiler set over high heat. Combine the chocolate and butter in the top half of the double boiler and set it on the bottom half. Heat, stirring frequently, until melted and completely blended, about five minutes. Remove from the heat and set aside.
Place the almonds and two Tablespoons of the stevia in the bowl of a food processor fitted with the metal blade and process until it resembles coarse sand. Do not overprocess or the nuts will turn to butter.
Scrape the almond mixture into the chocolate and add the almond meal, stirring to blend well.
Place the eggs in the bowl of a standing electric mixer fitted with the balloon whip. Add the remaining six Tablespoons stevia and beat on high until light yellow and tripled in volume, about seven minutes. Remove the bowl from the mixer and carefully fold the chocolate mixture into the eggs until there is no evidence of egg.
Pour the batter into the prepared pan and place in the preheated oven. Bake for 15 minutes; then, sprinkle the chopped almonds over the top. Continue to bake until the cake is set in the center, about 15 minutes more.
Remove the pan from the oven and place it on a wire rack to cool for 15 minutes.
Then, run a knife around the edge to ensure that the cake will easily come away from the sides. Remove the outside ring. Transfer the cake to a cake plate and set aside to cool completely before cutting into small wedges and serving.