Combine butter and canola oil in a large bowl and stir until well-combined.
Add sugar and stir again.
Add egg, egg white, and vanilla extract. Stir very well, until all ingredients are thoroughly combined, and then add buttermilk and stir again.
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 your chopped strawberries and continue to gently stir until ingredients are just combined.
Cover bowl with a dry towel and allow batter to sit 15 minutes**
Preheat oven to 425F (215C) and line a 12-count muffin tin with paper liners.
Once oven has preheated, portion batter into prepared tin, filling each liner all the way to the top with batter (without overflowing).
Bake on 425F (215C) for 8 minutes and then reduce the oven temperature to 350 (175C) (do not open the oven door or remove the muffins, just leave them in and reduce the temperature and bake another 12 minutes, or until tops are just beginning to turn golden brown.
Allow to cool, and, if desired, top with glaze.
Combine powdered sugar and 3 teaspoons of milk in a small bowl and whisk until smooth. If batter is too stiff to drizzle, add additional milk, one teaspoon at a time, until desired consistency is achieved (if you make the glaze too thin, just add more sugar).
Drizzle over cooled muffins and allow the glaze to set before enjoying.
*If you don't happen to have buttermilk, you can use this buttermilk substitute.**This is optional, it helps give the muffin tops a higher rise but you can certainly put them straight in the oven without waiting and they'll still taste delicious. Ideally you would let the batter set at least one hour, but I found 15 minutes gives me a decent rise (the muffins in the photographs were allowed 15 minutes) while still not dragging out the process too much.