Dissolve the yeast in half the milk. Put the flour in a bowl and make an indentation in the centre. Whisk in the yeast and milk mixture and leave to stand somewhere warm for 45 minutes.
After this time slightly warm the remaining milk and whisk in the egg yolk. Add to the previous mixture and mix in well, then leave to rest for another 45 minutes.
Beat the egg white until stiff and fold into mixture.
Very lightly oil a large frying pan and heat gently. Add small spoonfuls of the blini mixture and cook gently for about 1-2 minutes on each side, until lightly golden.