Cut off the ends of the Brussels sprouts and then cut in half. Lay them cut-side down and finely minced.
Place Brussels sprouts, spinach and 1/4 cup water in a microwavable-safe bowl. Cover and cook in microwave for 7-8 minutes until Brussels sprouts are soft.
Meanwhile in a saucepan on the stovetop, make the cheese sauce. Combine Greek yogurt, cheddar, Parmesan, garlic, mustard, almond milk, garlic powder, salt and pepper. Cook on low heat, whisking frequently, until cheddar is fully melted.
Remove Brussels sprouts and spinach from microwave and drain water from mixture, then combine with cheese sauce. Mix together well.
Pour pasta-vegetable mixture into an oven-safe dish and spread evenly. Top with almond flour and place under broiler in oven for 3-5 minutes until top is golden brown. Serve immediately.