For the compote:
Combine blueberries, sugar, butter, cinnamon stick and vanilla bean in a small saucepan and bring to a boil over high heat. Reduce heat and simmer to dissolve the sugar. Remove from the heat and stir in the cassis. Discard the vanilla bean and cinnamon stick. Serve at room temperature, folding in the chopped mint just before serving.
For the pancakes:
Mix together the flour, sugar, baking powder, baking soda and salt in a large bowl and set aside. In a separate bowl, combine the egg yolks, oil, buttermilk, lemon zest and vanilla extract.
Make a well in the center of the dry ingredients and pour in the liquid mixture. Mix together until flour is just incorporated.
In a small bowl, using a hand-held electric mixer, beat egg whites and cream of tartar until soft peaks form. Fold the egg whites into the batter just until incorporated. Let sit for 15 minutes, then gently fold in the blueberries.
Preheat oven to 200 degrees F.
Heat a nonstick pan or cast iron griddle over medium heat. Add a pat of butter and heat until the butter just begins to sizzle. Scoop a scant 1/4 cup of the batter into the pan or onto the griddle and cook until bubbles appear on the top surface and the bottom is golden brown, about 1 to 1 1/2 minutes. Flip over and cook until the bottom is lightly golden brown, about 45 seconds. Remove to a baking sheet and keep warm in a low oven. Repeat with remaining batter. Serve with syrup and compote and garnish with a dollop of ricotta.