In a small bowl, dissolve the yeast in the milk. In a separate bowl, combine the buckwheat flour, flour, eggs, yeast, sugar, salt and half the milk. Whisk smooth. Now add the remaining milk and beat again.
Cover the bowl with plastic wrap and allow to rest for an hour.
Melt butter in a frying pan. When it sizzles, add teaspoonfuls of the batter in circular movements to create the mini pancakes. Turn the poffertjes around as soon as the bottom has set, using two forks.
Serve Pancake Puffs with the best quality butter you can find and sieved powdered (icing) sugar.