In a large saucepan, bring 4 cups of water to a boil. Add the green tea leaves and baking soda. Boil for about 10-15 minutes until the water reduces to about half.
Remove the saucepan from heat and let the tea steep for an additional 5 minutes. Strain the tea into a bowl, discarding the leaves.
Return the strained tea to the saucepan and add the milk and salt. Bring the mixture to a gentle boil over medium heat.
Once boiling, reduce the heat and simmer for about 10 minutes, stirring occasionally. The tea should develop a rich pink color.
Stir in the heavy cream, sugar, and ground cardamom. Simmer for another 5 minutes, adjusting sweetness if necessary.
Remove from heat and let the chai cool slightly before serving. Pour into cups and garnish with chopped pistachios and almonds.