Deep and intense as your favorite brownie, these bars have a fraction of the fat. Serve them the day you bake them, preferably while still warm.
Preheat oven to 350 F. Coat 8-inch square baking pan with cooking spray. (Do not use glass baking pan or bars will get too dark and dry.)
In medium bowl, whisk together tofu and vinegar. Whisk in brown sugar, butter and vanilla until blended.
In large bowl, mix together flour, cocoa, baking powder and baking soda. Whisk in tofu mixture until just blended. Spread batter evenly in prepared pan.
Bake until cake pulls away from sides of pan and feels almost firm in center, about 25 minutes. Transfer to wire rack to cool until cake is firm enough to cut, about 30 minutes.
While in pan, cut into bars and serve. Or, to frost, invert cake onto a plate or cutting board. Spread ganache on warm cake and let stand until ganache is firm enough to cut without smearing, about 1 hour.