IMPORTANT: Make sure all your ingredients are at room temp (see notes at the bottom of the recipe)
Preheat your oven to 400ºF - Line a muffin tin with paper liners.
Sift together your flour, baking powder, baking soda, and salt. Set aside.
Cream together your butter and sugar in a medium bowl with your mixer until light and fluffy
Add in your egg and vanilla. Continue creaming until pale in color
While mixing on low, add in ⅓ of your flour mixture, then ⅓ of your buttermilk. Repeat two more times until just combined. Do not overmix.
Fold in your desired mix-ins such as fruit, nuts or spices.
Fill your liners all the way to the top with muffin batter. Top with more mix-ins if desired and sparkling sugar.
Bake for 15-20 minutes or until edges begin to slightly brown and a wooden skewer comes out cleanly when inserted into the center of the muffin.
Let your muffins cool in the pan for 10 minutes then move them to a cooling rack to cool the rest of the way.