Place the flours, sugar, salt and yeast into a large 2 litre jug, and mix the dry ingredients together.
Pour in the warm milk and the eggs. Use a whisk or large wooden spoon and mix the batter until it is lump free.
Cover the jug with a clean tea towel (or plastic food wrap), place in a warm area and allow to rise for about 1 hour or until almost doubled in size.
Give the batter a quick mix, then pour some of the batter into a plastic squirt bottle. <-- see note 3
Heat up a poffertjes maker and brush butter in the holes. Use the squirt bottle to fill each hole to the top with batter. Cook them until the bottoms start turning brown and the batter on the top has firmed up. Use a skewer to flip the poffertjes over and allow to cook for a minute or two. Remove from the poffertjes maker and transfer to a plate. Repeat the process for the remaining batter.
Serve hot sprinkled with icing sugar and butter, or with jam and cream.