Add the sweetened condensed milk to a small saucepan over low heat. Warm gently until hot but not boiling.
Whisk in the pistachio butter and white chocolate until completely melted and smooth.
Add the half & half and salt, and stir until fully incorporated. Remove the saucepan from the heat, and stir in the vanilla and almond extracts.
Transfer to a mason jar or airtight container and use the sauce in any recipe right away, or let cool completely before adding a lid, and storing in the refrigerator for up to 2 weeks (or until the best by date on your half & half).