Preheat the oven to 425°F (220°C). Place a 9-inch oven-safe skillet inside the oven to heat while you prepare the batter.
Pour the aquafaba into a mixing bowl and whisk vigorously by hand or with a hand mixer for about 30 seconds, just until lightly foamy.
Whisk in the plant milk, vanilla extract, brown sugar, and salt until fully combined.
Whisk in the flour and baking powder until you have a thin, smooth, lump-free batter. The consistency should resemble crêpe batter.
Carefully remove the hot skillet from the oven. Add the vegan butter and swirl to coat the bottom and sides completely.
Immediately pour the batter into the hot skillet. Return it to the oven and bake for 20-22 minutes, until puffed and lightly golden around the edges. For a more deeply golden and crispy finish, switch the oven to broil for the last 1–3 minutes. Keep the skillet on the middle rack and watch closely to prevent burning.
Remove from the oven and serve immediately, dusted with powdered sugar and topped with fresh berries.
Notes
To store: German pancakes are best served immediately, but leftovers can be stored in the refrigerator for up to 2 days.
To reheat: Warm in a 350°F oven or skillet until heated through. The microwave also works, but the texture will change.