Add berries to a blender cup or tall bowl. Blend with the immersion blender a few seconds to make a thick compote. Transfer to another bowl and rinse the blender cup.
Add the banana, milk, melted butter and vanilla to the blender cup or tall bowl. Using an immersion blender, blend until smooth.
Add the buckwheat flour, baking powder, baking soda and salt. Blend until combined and smooth.
Heat a non-stick skillet over medium-high heat. Melt a small amount of butter, enough to lightly cover the skillet. The skillet is warm enough when a drop of water sizzles.
Transfer ΒΌ cup of the batter to the skillet. Spread it to form a round pancake (it should be lightly thick). Cook until you see some bubbles at the top and the edges are firming up. Flip and cook for another 1-2 minutes.
Serve with the berry compote and other toppings of choice.