In a medium saucepan, cook the blueberries on medium-low heat, 8-10 minutes, stirring frequently. Strain the blueberries with a fine mesh sieve until ¼-1/2 cup of juice drains. Set the juice aside.
Return the blueberries to the pan and add the vanilla extract, lemon juice, ground cinnamon, and maple syrup. Stir for 1 minute more. Sprinkle the chopped chocolate over the blueberries and stir constantly until fully melted. Remove from heat, taste test, and make adjustments to your preference, if needed (i.e., add more maple syrup for more sweetness, etc.). Pour into individual ramekins until each is three-quarters full with the compote.
Preheat the oven to 375℉. In a separate bowl, whisk together the dark brown sugar, all-purpose flour, unsweetened cocoa powder, ground cinnamon, and salt. Drizzle in the melted butter a bit at a time and stir and fluff the mixture with a fork. Repeat until all the butter is used, then switch to your hands until the sugar clumps to your liking. Generously cover the ramekins in streusel topping.
Bake for 10-15 minutes, or until the compote begins to bubble. Allow to cool to a reasonable temperature before serving.
