Place a 12-cup or two 6-cup muffin tins in oven and preheat oven to 425° (with muffin tins in oven).
Melt the butter needed for the pancake batter and set aside to cool slightly. Meanwhile, combine pancake ingredients in a blender (or a medium bowl with an immersion blender), adding the cooled, melted butter last. Mix well, until frothy. Leave to stand in blender (or bowl) while oven preheats.
When oven is pre-heated, melt the butter for the pan. Remove hot muffin tins from oven and quickly pour a bit of melted butter into each muffin cup. Turn blender on for a few seconds to re-mix the batter, then quickly pour in to hot muffin cups, dividing equally between 12 cups, filling about 1/2 full.
Place in oven and bake for 22-24 minutes, or until puffy and deep golden colour. Remove from oven. Pancakes will quickly deflate, but that's what they do. Remove from pan to a cooling rack to cool slightly before serving. (They should come out easily if the muffin cups were well brushed with butter. If not, run a knife around the edges, then use a fork to lift them out).
Serve with a pat of butter, maple syrup and some chopped walnuts or pecans, if you like. Garnish with icing/confectioners sugar.
Notes
These mini dutch baby pancakes freeze well. To re-heat, simply place frozen dutch babies on a baking sheet or back into a muffin tin and loosely cover with a piece of aluminum foil. Place into pre-heated 350 oven until warmed through, 10-15 minutes. Alternately, you can microwave until warm.