Bring 1 liter milk to a gentle boil in a heavy pan, stirring so it does not scorch.

Reduce heat to low. Add lemon mixture in splashes, stirring, until whey separates and curds look clear. If needed, add a teaspoon more lemon water.

Pour through a cheesecloth-lined sieve. Rinse very gently under cool water to remove lemon tang. Gather cloth, twist, and hang 25 to 35 minutes until moist but not dripping.

Transfer chenna to a wide plate. Knead with the heel of your hand for 6 to 10 minutes until the mix feels smooth and fat-free on your fingers, not crumbly.

Divide into 10 to 12 equal portions. Roll each into a smooth ball, then flatten into a disc about 2 cm thick. No cracks on the edges.

Combine water and sugar in a wide pan. Bring to a boil, then reduce to a steady simmer. Syrup should feel thin, not sticky between fingers.

Add discs in a single layer. Cover with a tight lid 5 minutes, then uncover and flip gently. Simmer 6 to 8 minutes more until discs look puffed and spring back slowly when pressed.

Cool discs in syrup 10 minutes, then lift with a slotted spoon and press lightly between two spoons to remove excess syrup (do not crush).

Simmer the second liter of milk on medium-low, scraping sides often, until reduced by roughly one third and the milk looks slightly thicker. Stir in sugar, saffron milk, cardamom, and half the pistachios. Cook 4 to 6 minutes more until silky. Cool to room temperature, then chill if you prefer cold rasmalai.

Slide discs into the milk bath. Rest at least 2 hours in the fridge, spooning milk over the tops once or twice. Garnish with remaining pistachios and rose water if using.