Bring milk to a gentle simmer in a pot. As the milk comes to a boil, grind cardamom and cinnamon with a spice grinder or mortar and pestle until finely ground.
Add cashews, ground spices, and sugar to the simmering milk. Keep it at a gentle simmer (~ medium-low heat) for about 30 minutes.
Soak saffron in *warm* oat milk to enhance its flavor.
Let the contents of the pot cool a little before blending until smooth.
Pour into a mixing bowl. Use an electric hand mixer to whip on high speed for 2 minutes. Place the bowl in the freezer for 30 minutes. Whip again for 2 minutes. Place the bowl in the freezer for 30 minutes. Whip again for 2 minutes.
After the third round of whipping, fold in the saffron, pistachios, and almonds. Pour into a freezer-safe container and freeze for at least 4 hours.
Before enjoying, allow the ice cream to soften at room temperature. I find that 30 minutes works best for me, but find what works for you!