2 cups (12 oz.) fresh red currants, tossed with 2 tsp flour
For the streusel:
3 TBS butter, room temperature
3 TBS brown sugar
3 TBS white sugar
1/4 cup flour
1/4 tsp ground cinnamon
Make the cake: Preheat the oven to 375F. Butter and lightly flour a 9 inch cake pan or springform pan. Tap any excess flour out over the sink. Set prepared pan aside.
Whisk together the flour, baking powder, and salt in a medium bowl. Set aside.
Add the softened butter and the sugar to the bowl of a mixer and beat on medium until light and fluffy. Beat in the eggs one at a time, beating just until they are incorporated, then stopping the mixer. Add half of the flour mixture to the butter-sugar-egg batter and beat just until incorporated. Now add the milk and beat on low just until incorporated. Add the remaining half of the flour mixture and beat until incorporated. Remove the bowl from the mixer – you’ll do the rest by hand.
Stir in the vanilla extract until it is evenly mixed into the batter. Add the flour-coated currants (the light flour coating helps prevent them from sinking when mixed into the cake) and gently stir until they are evenly distributed throughout the batter. Use a spatula to scrape the batter into the prepared cake pan. Smooth out gently so the batter is level.
Make the streusel: In a small bowl, use your fingers to mix together the butter, brown sugar, sugar, flour, and cinnamon until it forms a crumbly mixture with pieces the size of peas. Sprinkle over the top of the cake batter.
Bake the cake: Transfer the cake to the pre-heated oven and bake until a toothpick inserted in the center comes out clean and the top of the cake is golden brown, about 50-60 minutes. Remove from oven. Let cool for 15 minutes, then remove from the pan, slice, and serve warm.