Dissolve the sugar. Mix the sugar or panela with the hot water and stir until completely dissolved. The water should be very hot (freshly boiled) — that's what lets the sugar dissolve without leaving any graininess.
Add the milk powder. Add it to the sugar water and blend (regular or immersion blender) until you have a smooth, lump-free cream. Doing it by hand is a struggle: the blender is what makes the difference here.
Let it rest. Wait a few minutes: it thickens quite a bit as it sits. If you want it even thicker, half an hour in the fridge and it's ready.