Combine the flours, eggs, milk, salt and groats in a medium bowl and whisk together. This should be done on the day before making the buckwheat pancakes - for me this is usually Friday evening.
Cover the bowl and place in the fridge overnight.
Next morning, take the batter out of the fridge and give it a good whisk.
Get ready to make the pancakes by heating a pan over a medium heat.
Add a little bit of butter to cover the base of the pan. I use a silicone brush to distribute the butter across the base of the pan. It'll make moving and turning the pancakes easier.
Add a ladle full of pancake batter to the hot pan and move from side to side until evenly distributed.
Brown on one side before flipping over.
Remove and set aside (keep warm in the oven until the others are done, cover the pancakes to prevent them from drying out).