Pre-heat the oven to 400°F. Grease a 9x9 baking dish with butter or oil of choice and set aside.

In a large saucepan, heat the butter over medium-high heat.

Add onion and garlic and cook until onion is translucent about 5 minutes.

Add spices and cook for one minute until fragrant.

Add arrowroot flour and stir for one minute until well combined.

Pour in cashew milk. Mix well. Bring sauce to a boil. Once at a boil, lower heat and let simmer until thick enough to coat the back of a spoon.

Add in 1/2 cup of parmesan cheese (if using) and whisk until cheese has melted, about 30 seconds. Make sure the mixture has thickened a good amount before adding spinach.

In batches, add spinach (and kale if using) to the sauce until the greens start to wilt. Taste and adjust seasoning as needed. Take off heat.

Pour spinach/kale mixture into a greased 9x9 casserole dish and top with remaining parmesan cheese. Bake for 20 minutes or until bubbly and the cheese on the top is a golden brown.

Serve warm!