Potato casserole with mushrooms

Ingredients:

• Cooking spray for greasing the pan
• 340 g Greek yogurt, 2% fat
• 1 cup skim (1%) milk
• 1/2 cup low-fat sour cream
• 3 tbsp unbleached wheat flour
• 1.1 kg frozen or fresh grated potatoes (defrost, if fresh squeeze out excess liquid)
• 1 cup (110 g) coarsely grated very sharp cheddar cheese
• Coarse salt and freshly ground black pepper
• 2 tbsp (30 g) unsalted butter
• 2 large onions, chopped
• 450g sliced ​​cremini mushrooms (brown button mushrooms)
• 3 crushed cloves of garlic
• 2 tbsp. Panko breadcrumbs (traditional Japanese breading mixture for deep-frying)
• 1/4 tsp ground nutmeg (optional)
• 1-2 tbsp chopped parsley or chives, for garnish

Preparation:

1. Preheat oven to 375°F (190°C). Spray a 9 x 13-inch baking dish with cooking spray.
2. In a large bowl, whisk together the yogurt, milk, sour cream, and flour. Stir in the grated potato, 1/2 cup of cheddar, 2 teaspoons of salt, and 1/2 teaspoon of pepper. Set aside.
3. In a large skillet, melt the butter over medium-high heat. Add the onion and cook, stirring constantly, until softened and golden, about 10 minutes. Add the mushrooms and cook, stirring constantly, for another 10 minutes, until the mushrooms release their juices and the onions begin to brown. If the pan gets too hot, add a little water. Add the garlic and cook for 1 minute. Add the vegetables to the potato mixture and toss.
4. Spread the mixture evenly over the prepared pan. Sprinkle with the remaining cheese (1/2 cup), breadcrumbs, and, if using, nutmeg. Bake until golden brown, about 45 minutes.
5. Sprinkle the casserole with parsley before serving.