Always use a From-Scratch muffin recipe, never boxed!
Never use a mixer to incorporate your dry ingredients to your wet. Use a spatula or spoon. Do not over mix your batter.
Cover your batter tightly and refrigerate for at least 1 hour (can go overnight as well).
Preheat your oven to 425F. Yes, I know the recipe calls for 350 but trust me on this. I typically bake my muffins in the upper third of the oven. You see placing the muffins in the upper third of the oven it tends to be hotter and the heat more constant. You can most certainly use the middle rack as well if you want.
Spray the top of your muffin pan with non-stick spray. Line the pan with cupcake/muffin liners.
The batter will be THICK. You can gently stir it first. Just try not to deflate it. Fill the muffin papers almost ALL THE WAY TO THE TOP OF THE PAPER. (just leave about a 1/8″ from the top). Yes I know, it’s spilled over before but this works.
If you have empty cavities in your muffin tin (not enough batter), remove the liner and add 1/2 cup water in each.
Bake 6-9 minutes at 425. The muffins should be about a 1/4″-1/2″ above the paper. That’s the sign the heat can be turned down.
Reduce heat to 350 (DO NOT OPEN THE DOOR TO DROP THE TEMP.. sorry for the YELLING.. lol) and bake for 6-10 minutes or until a toothpick inserted comes out barely clean (crumbs are OK). *Note: this will depend on your actual recipe.
Remove from the oven and cool in the pan on a rack for 1-2 minutes.
Remove the muffins (they will be hot) from the pan and cool on the rack. Do not leave them in the pan to cool completely as the bottoms and sides will become soggy. Leaving them in the pan builds up too much moisture.
Notes
I do NOT use boxed muffin mixes – ever nor would I recommend using this technique on a boxed mix.
The reason why this works is the initial high heat of 425 degrees F causes the batter to have greater oven spring or the rapid rise during the first few minutes of baking. The higher heat creates a burst of steam that lifts the batter.