Step 1: Preheat your oven to 400°F (200°C). Prepare a 12-cup muffin tin by lining it with paper liners or greasing it thoroughly with cooking spray.
Step 2: In a large mixing bowl, whisk together the all-purpose flour, baking powder, and salt until they are well combined. This ensures even distribution of the leavening agents.
Step 3: Gently fold in the shredded cheese and the chopped fresh herbs into the dry mixture. Make sure they are evenly coated, which helps prevent them from sinking to the bottom during baking.
Step 4: In a separate, medium-sized bowl, whisk together the milk, large egg, and melted unsalted butter until the mixture is smooth and homogenous.
Step 5: Pour the wet ingredients into the bowl containing the dry ingredients. Stir gently with a spoon or spatula until just combined. A few lumps are okay; overmixing will lead to tough muffins. If you're adding optional diced vegetables like bell peppers or spinach, fold them in now.
Step 6: Divide the muffin batter evenly among the 12 prepared muffin cups, filling each cup about three-quarters full.
Step 7: Bake the muffins in the preheated oven for 15-20 minutes, or until they are golden brown on top and a toothpick inserted into the center comes out clean.
Step 8: Once baked, remove the muffin tin from the oven and let the muffins cool in the pan for 5 minutes. Then, transfer them to a wire rack to cool completely. Serve warm for the best experience, or at room temperature.