In a 10-inch cast iron skillet or baking dish, add 1 tablespoon butter. Let it soften at room temperature.
Preheat the oven to 400˚F (200˚C).
In a small bowl, whisk together the flour, cocoa powder & salt. Set aside.
In a blender, add milk, sugar, eggs and vanilla. Blend until smooth, about 20 seconds. Add the flour mixture and pulse until just incorporated, about 5 – 7 pulses.
Coat the 10-inch skillet with the softened butter. Add the pitted cherries and arrange them in a single layer. Pour the batter over the cherries. Top with the chocolate chunks. Bake in the oven until puffed around the edges and set in the center, about 35 minutes. Remove from oven and let it cool for about 15 minutes. It will sink slightly as it cools.
Scoop the clafoutis into serving plates. Serve warm with whipped cream and chocolate curls if desired.