Steam the potatoes and cauliflower until very tender, about 20 minutes.
Add the potatoes and cauliflower to a food processor along with salt, and process until light and fluffy. The cauliflower has enough water that no butter or milk is needed for the mixture. Set aside.
In a large skillet, heat up 1 tablespoon olive oil on medium high heat. Add onion, garlic, rosemary, salt and pepper, and saute for 7-10 minutes, until just beginning to brown.
Add the ground beef, and brown, while stirring to break up the meat, about 10 minutes.
In a small bowl, add beef broth, tomato paste, coconut aminos, and arrowroot powder, and whisk together until combined well.
Add the beef broth mixture over the ground beef, and bring to a low simmer over medium heat.
Add the carrots and snap peas, and stir to combine, and then remove from heat.
Add the ground beef and vegetable mixture to the bottom of a 9x9 or 8x10 casserole pan.
Top the mixture with the cauliflower-potato mixture, spooning out big scoops and placing them on the corners of the casserole. Use a spoon to smooth the potatoes into an even layer. Top with more rosemary and black pepper, if desired.
Bake in the Sharp Superheated Steam Countertop Oven on 400º F on the Bake/Reheat function for 14 minutes, or until the top has begun to brown. If you've refrigerated the casserole prior to baking, it will take an extra 5-8 minutes to fully heat through.
If using a conventional oven, preheat the oven to 400º F, and bake the casserole for 22 minutes, until the top has begun to brown.