This seems to work (measured by volume):

Dry

• 80 parts flour (100 by weight)
• 20 parts milk powder (25 by weight)
• 4 parts sugar (8 by weight)
• 1-2 parts baking powder (2 by weight)
• 1 part salt (2 by weight)

Wet

• Water

Mix dry together and store. When ready to use, mix with water to make thick batter.