Creamed Brussels Sprouts

Heat oven to 375°. In a large skillet over medium heat, heat oil. Add onions and cook until soft, 6 minutes. Add garlic and cook until fragrant, 1 minute. Add Brussels sprouts and red pepper flakes and cook until tender, 7 minutes more. Season with salt and pepper, then remove from heat and let cool. In a large bowl, stir together Greek yogurt, mayonnaise, eggs, and lemon zest, and cheeses and season with salt and pepper. Fold in cooled vegetables and transfer to a medium baking dish.  Bake until top is golden and cheese is bubbly, 30 to 35 minutes.  Garnish with parsley, Parmesan, and red pepper flakes and serve immediately.