Grease or rinse a heavy bottom pot and pour milk to it.
Bring it to a boil then reduce the flame to low. Let the milk simmer until it reduces approximately to half the original quantity (to 3 cups).
While the milk simmers, bring 1 cup water to a boil in a small pot. Add almonds and pistachios.
Turn off the heat and rest the nuts until the skin loosens (for about 10 to 15 mins). Drain them and peel the skin. Chop them finely and keep aside.
Transfer 2 to 3 tablespoons of hot milk from the pot to a small bowl. Add saffron strands and leave them to soak.
If you do not want to have layers of cream in your rabdi, you can skip this step. After simmering the milk for a while, a layer of cream forms on top of the boiling milk. Gently move that to the sides of the pot and stick up. (check the step-by-step pictures above or video)
Next stir once to prevent the milk from getting scorched at the bottom.
Continue to simmer the milk, slide the layer of cream to the sides of the pot every time it forms and repeat sticking it up to the side. Stir again once. This process of sliding and sticking to the sides should happen every time a layer of cream forms until the milk reduces to half the original quantity. I.e 3 cups in this case.
Do not forget to stir at the bottom every time you slide the cream.
When the milk reduces to half, add sugar and then scrape off the layers of cream from the sides of the pot. If the milk cream has dried up, pour some hot milk (from the pot) over the sides. This will soften it and loosen. Add it back to the milk.
Simmer until the quantity reduces to 2 cups. Add nuts, saffron milk, cardamom powder & rose water. Turn off the heat.
Chill rabri and garnish with nuts just before serving. It can be served with gulab jamun, malpuas & jalebi.