Combine butter and neutral cooking oil in a large bowl and whisk until well-combined.

Add sugar and whisk to combine.

Add egg, egg white, and vanilla extract. Whisk vigorously until all ingredients are thoroughly combined.

Gradually whisk in buttermilk until completely combined.

In a separate bowl, whisk together flour, baking powder, corn starch, and salt.

Fold the dry ingredients into the wet gently, taking care not to over-mix the batter. Once about half of the dry ingredients have been combined, add chopped strawberries and continue to gently stir until ingredients are just combined.

Optional: Cover bowl with a dry towel and allow the batter to rest for 30-60 minutes. Preheat your oven to 425?F (215?C) during this time.

Line a 12-count muffin tin with paper liners. Evenly divide batter into the prepared tin (for bigger muffins, use only 9 liners).

Sprinkle a small bit of sugar over the top of each muffin.

Transfer to the center rack of the preheated oven and bake for 8 minutes, then reduce the oven temperature to 350?F (175?C) and bake for another 10-12 minutes, or until the tops are just beginning to turn golden brown.

Allow muffins to cool in the tin for 5-7 minutes before transferring to a cooling rack to cool completely.