In a stainless steel pot, combine 4 cups cold water, green tea leaves, baking soda, crushed cardamom, and cinnamon stick. Bring to a rolling boil over medium-high heat.

Reduce heat to medium-low and simmer vigorously for 10-15 minutes, until the liquid reduces by almost half and turns a deep ruby-red color. This is your concentrated 'Kawha'.

Remove from heat. Vigorously pour the tea from a height back into the pot (or between two cups) for 2-3 minutes to aerate and create initial froth. This is the 'cho'ch' technique.

Add the 1/2 cup of water to the aerated tea. Return to medium heat and bring back to a boil for 2-3 minutes.

Strain the tea through a fine-mesh strainer into another pot or bowl, pressing gently on the solids. Discard the leaves and spices.

Return the strained tea concentrate to a clean pot. Add the milk and salt. Heat over medium-low until steaming hot and just beginning to simmer at the edges. Do not boil.

Perform a final aeration by pouring the tea between vessels a few times to build a creamy froth. Stir in soaked saffron and its liquid (if using).

Pour into cups. Top with froth, garnish with crushed nuts, and serve immediately with traditional breads or biscuits.