The same flavanoids that lower the risk of stroke reduce blood pressure, albeit slightly. A review from the Cochrane Collaboration found that in 20 different studies, those who ate between 3 and 100 grams of dark chocolate or cocoa powder each day lowered their blood pressure a little bit, usually from 2 to 3 mg Hg.
As always, a bar of dark chocolate is the superhero here. “Having dark chocolate as part of a dessert often means you're enjoying it alongside saturated fats and sugars.