Step 1: Preheat and Prepare

First, preheat your oven to 400°F (approximately 200°C). Promptly setting this up ensures the oven is at the right temperature when the muffins are ready to bake. Prepare your muffin tin by lining it with paper liners or lightly spraying with nonstick cooking spray to prevent sticking once baked.

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Step 2: Combine the Dry Ingredients

In a large mixing bowl, start by combining your dry ingredients—2 cups of flour, 1 tablespoon baking powder, ½ teaspoon salt, and 1/8 teaspoon ground cinnamon. The cinnamon is a subtle but important addition that enhances the chocolate flavor, making it richer without overwhelming the taste.

Gently whisk the dry ingredients together until evenly mixed. This ensures the baking powder and spices are distributed uniformly throughout the flour base.

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Step 3: Coat the Chocolate Chips

Take the 12 oz bag of milk chocolate chips and toss them lightly with a spoonful of the dry flour mixture. Coating the chocolate chips in flour helps prevent them from sinking to the bottom of the muffins as they bake, allowing every bite to have evenly distributed chocolate.

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Step 4: Mix the Wet Ingredients

In another bowl, combine all your wet ingredients for an easy one-bowl process. Add ½ cup melted unsalted butter, 2/3 cup whole milk, 2 tablespoons sour cream, 2 eggs, and ½ teaspoon vanilla extract.

Next, add both 1/3 cup granulated sugar and 1/3 cup brown sugar to the wet mixture. Stir everything together until the sugars dissolve and the mixture is smooth. The sour cream is a secret ingredient that adds moisture and tenderness, giving these muffins a wonderfully soft texture.

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Step 5: Gently Combine Wet and Dry Ingredients

Pour the dry ingredients into the bowl with the wet ingredients. Using a spatula or wooden spoon, fold the two together carefully. Mix just until combined—avoid overmixing, which can develop the gluten in the flour and make the muffins tough rather than tender.

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Step 6: Add in the Chocolate Chips

Fold the flour-coated chocolate chips gently into the batter. This step ensures every muffin is packed with melty chocolate morsels without breaking up the chips too much.

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Step 7: Portion the Batter into the Muffin Tin

Using an ice cream scoop or large spoon, evenly distribute the batter into the prepared muffin tin cups. This method ensures uniform muffin sizes and even baking. Fill each cup about three-quarters full to allow room for the muffins to rise.

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Step 8: Bake Your Muffins

Place the muffin tin in the preheated oven at 400°F and bake for 15 to 18 minutes. Around 15 minutes, start checking doneness by inserting a toothpick in the center of a muffin. When it comes out clean or with just a few moist crumbs (no wet batter), the muffins are ready. Be careful not to overbake, which can dry them out.

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Step 9: Cool and Enjoy

Once done, remove the muffin tray from the oven and let the muffins cool in the tin for about five minutes. This resting time lets the structure set slightly, making them easier to remove and handle without breaking.