If using regular yogurt, strain it through a cheesecloth or muslin cloth for a few hours or overnight to remove excess whey and obtain hung curd. If using Greek yogurt, skip this step.
Preheat the oven to 250°F. In a large bowl, combine ¼ cup hot water and ½ cup sugar, whisking until the sugar dissolves. Add 1 cup matchstix carrots to the bowl and toss gently to coat.
In a small bowl, soak the saffron threads in ¼ cup warm milk. Let it sit for about 10-15 minutes to release its color and flavor.
In a high-powered blender, combine the saffron milk with the remaining 1 cup matchstix carrots. Blend until completely smooth, about 1 minute.
In a large mixing bowl, combine the yogurt, blended carrots, ¼ cup sugar, and ground cardamom. Mix well until everything is thoroughly combined and the sugar is dissolved. Cover the bowl with plastic wrap or a lid and refrigerate the shrikhand for at least 1-2 hours to allow the flavors to meld and to chill.
Before serving, give the shrikhand a good stir. Divide it into serving bowls or glasses. Garnish each serving with chopped pistachios and rose petals.