Preheat oven to 350. Line a 8x8 square pan with buttered parchment paper.
In a small double boiler, or in the microwave, melt the chocolate and butter.
In a food processor, pulse the black beans until well blended. Add the remaining ingredients, except chocolate. When all is blended, pour the chocolate into the top of the food processor and blend again.
Pour the batter into the pan. Bake until done.
In a bowl, cream the cheese and sugar. Melt the chocolate and margarine; add vanilla, pour into the cream cheese mixture and beat until smooth.
Frost the brownies when cool. The brownies and the frosting will firm up as they cool. They will be dense and delicious.