Cozy Autumn Breakfast Casserole

Bahan-bahan (12 porsi)

• 8 ounces baby bella mushrooms, quartered
• 1.5 pounds potatoes, diced into 1/2-inch cubes (I used half sweet potatoes, half Yukon gold)
• 1 large red bell pepper, cored and diced
• 1 medium white or yellow onion, peeled and diced
• 3 tablespoons olive oil
• sea salt and freshly-cracked black pepper
• 1 pound ground Italian sausage (or breakfast sausage)
• 4 cloves garlic, peeled and minced
• 2 handfuls roughly-chopped fresh kale, tough stems discarded
• 15 eggs, whisked
• 2/3 cup milk
• 1 1/2 tablespoons Old Bay Seasoning, or more/less to taste