Preheat your oven to 425°F. This high temperature is crucial for that initial rise that makes the muffins so fluffy. While the oven is heating up, grease a 12-count muffin tin with nonstick spray or line it with paper liners. If you have two muffin tins, prepare four muffin wells of a second tin. Set aside.
In a large bowl, whisk together the all-purpose flour, baking powder, baking soda, and kosher salt. This mixture will be the base of your muffins, so be sure to combine them well to avoid any lumps. Set aside.
In another bowl, whisk the melted butter, vegetable oil, granulated sugar, and eggs together. It should be a smooth mixture. Now add the buttermilk and vanilla extract, whisking until everything is well combined.
Pour the wet ingredients into the dry ingredients. Gently mix just until combined. Be careful not to over-mix, as this can lead to tough muffins. It's perfectly okay if there are a few small lumps in the batter.
Now, it’s time to fold in the semisweet chocolate chips. Use a spatula to gently incorporate them into the batter, ensuring even distribution throughout.
Using a portion scoop, fill each muffin well with batter, about two-thirds full. If you’re using two muffin tins, fill all 16 muffin wells. If you're using just one tin, cover the bowl of remaining batter and set aside for later.
If desired, sprinkle the tops of the muffins with coarse sugar. This small touch adds a wonderful crunch and sweetness to the muffins.
Place the muffin tin in the preheated oven and bake at 425°F for 5 minutes. This high heat will help the muffins rise. After 5 minutes, keep the muffins in the oven but reduce the temperature to 350°F.
Continue to bake for an additional 16 to 18 minutes, or until a toothpick inserted into the center of a muffin comes out clean. Keep an eye on them to ensure they don’t over-bake!
Once baked, let the muffins cool in the pan for 10 minutes before transferring them to a cooling rack to cool completely. For any remaining batter, repeat the baking process. Serve warm, and enjoy every bite!
