Preheat the oven to 350 degrees F (175 degrees C). Spread walnuts, almonds, and pistachios on a rimmed baking sheet.
Bake nuts in the preheated oven until toasted and fragrant, 10 to 15 minutes.
Transfer to a food processor while still hot; process at high speed until broken down and starting to clump together. Turn off processor and scrape down sides with a spatula. Begin processing again until a cream starts to form. Add sucralose, honey, vanilla extract, and salt; blend for 1 minute more.
Add cocoa powder gradually, alternating with milk powder, and process for 1 minute more. Let cool completely. Scoop into a jar and refrigerate.
