Combine milk, water, crushed cardamom pods, vanilla bean seeds, and the scraped vanilla pod in a medium heavy-bottomed saucepan. Set over medium heat and warm until the milk just begins to steam, about 5 minutes. Do not boil.

Add the rinsed arborio rice and stir to combine. Reduce heat to medium-low.

Cook uncovered for 25 to 30 minutes, stirring every 3 to 4 minutes, until the rice is tender and the mixture has thickened to a loose, creamy consistency. It should fall slowly from the spoon.

Stir in the sugar and salt in the last 5 minutes of cooking. Taste and adjust sweetness.

Remove from heat. Fish out and discard the vanilla pod and cardamom pods.

Spoon into bowls while warm. Top with chopped pistachios and a drizzle of honey if using. Serve immediately, or press plastic wrap onto the surface and refrigerate for up to 4 days.