Preheat oven to 350 F. and butter and cocoa powder a 9-inch square baking pan, knocking out excess cocoa. (As noted in an earlier recipe, using flour for a chocolate item leaves a white residue; much better to use cocoa. Plus, you get an extra layer of chocolate! Hard to beat.)
Melt butter and chocolate in the microwave, starting with 2 minutes on 50% power. Use the mixing bowl you're going to use to mix up the batter. If you're using the oil and cocoa instead of the unsweetened chocolate, stir that in after the bittersweet chocolate is melted. Set aside to cool while you proceed.
In a food processor process sugar and almonds until ground fine. Stir almond mixture into chocolate mixture and add eggs, 1 at a time, beating well until mixture is glossy and smooth. Stir in flour, salt, and cinnamon until just combined.
Spread batter evenly in pan and bake in middle of oven 20 minutes, or until a tester comes out with crumbs adhering to it. You may need another 5 minutes or so. Cool brownies completely in pan on a rack before cutting into 16 squares.
These are seriously rich, dark, and fudgy. The ground almonds add a nice texture.