Ham and Mushroom Muffins [and Cheddar Cheese, too!] - Cooking by the Book

Ingredients

• ½ stick (50 g) unsalted butter
• ½ small onion, finely chopped
• 1 cup (80 g) chopped button mushrooms
• 3 cups (360 g) all-purpose flour
• 2 ½ teaspoons baking powder
• 2 cups (250 g) firmly packed grated Cheddar cheese
• 1 cup (220 ml) whole milk
• 1 egg
• 2 ¾ ounces (80 g) smoked ham, finely chopped
• Sea salt and freshly ground black pepper