Continue pouring in the milk until the batter is the consistency of slightly thick single cream. You don't want it to be too runny, because you will have troble cooking the pancakes. You can always add more milk after you've cooked the first 2-3.
For thicker pancakes, the batter will be more dense, for thinner pancakes, it will be less dense.
Incorporate 50 ml oil, cinnamon and rum flavour (or any flavour you wish) and mix everything very well.
If there are still lumps in the batter, use the mixer or the blender to smooth them.