Pulse the cashews in a blender until a fine powder forms. You’re looking for a flour-like consistency. Be careful not to overmix or you’ll end up with cashew butter.
Add the almond milk, garlic, salt, lemon juice and mustard. Blend on high until smooth.
Pour the liquid into a 4-quart slow cooker. Add the spinach, artichoke hearts, water chestnuts, and nutritional yeast (if using). Stir until well combined.
Cover and cook on high for 2 hours or low for 3-4 hours, or until warm and bubbly.
Uncover and stir in the mayonnaise or veganaise. If the dip seems dry, add an extra splash of almond milk. Taste and add additional salt or freshly ground pepper to taste. Serve warm or at room temperature.
*Nutritional yeast adds a cheesy flavor without containing any dairy. Find it on the bulk aisle of your natural foods store, or in the baking section. If you can't find or don't want to use it, feel free to omit.**Avocado mayonnaise is made with avocado oil and is usually free of canola and soy oil, which is why I prefer it over regular mayo.Veganaise is an egg-free, vegan alternative to mayo, and is a great choice if you're avoiding eggs or want to keep this recipe vegan.Want to turn it into a main dish by adding chicken? See this instant pot spinach artichoke chicken recipe here!