Peel and grate ginger. Squeeze grated ginger pieces to release juice; measure 2 teaspoons ginger juice and transfer to a bowl.
Place milk in a saucepan; heat until temperature reaches 160 degrees F to 170 degrees F (71 degrees C to 77 degrees C), about 5 minutes. Add sugar and stir until dissolved; pour into the bowl with ginger juice. Stir mixture immediately and cover with a small plate. Cover the covered bowl with a clean towel; let sit for at least 7 minutes.