It's important that everything is softened to room temperature. If you need to, place the cream cheese (with the packaging) and the egg in a bowl of hot water for 5-10 minutes and microwave the sour cream for 10-20 seconds.
Place the cream cheese with the pistachio paste and sugar in the bowl of your stand mixer, fitted with the paddle attachment (or a large bowl with a hand mixer). Turn the mixer to low speed and mix for 1-2 minutes, scraping the edge of the bowl every so often to make sure the mixture is smooth and there are no chunks of cream cheese left.
1/3 cup (67g) granulated sugar, 1/4 cup (60g) pistachio paste, 8 oz (1 brick) cream cheese
Add the sour cream, vanilla and salt and mix at low speed, until they're fully combined. Then add the egg and mix just until it's fully combined.
1/4 cup (60g) sour cream, 1 tsp vanilla bean paste, 1/4 tsp fine sea salt, 1 large egg
Scrape the edge of the bowl well and give it one more good mix. Make sure to get smooth out any visible chunks and don't increase the speed so you don't incorporate air.
Fold the batter a few times before pouring it over the crust. Place the cheesecake on the middle rack of the oven and place another pan full of hot water next to it.
Bake for 35 minutes. The edges of the cheesecake should be set but the center should still be jiggly.
Turn the oven off and leave the door a little open for 10 minutes. Then open the door of the oven all the way for another 10 minutes.
Remove the cheesecake from the oven and allow it to cool to room temperature for a couple of hours. Then refrigerate for at least 6 hours before serving.