In the bowl of an electric stand mixer, or in a large bowl with a hand mixer, mix together the sugar and lemon zest for 30 seconds on medium speed.
Add the butter and oil and mix on medium speed for 1-2 minutes until the mixture is light and fluffy. Add the egg and mix until combined.
Whisk together the flour, salt, baking powder and baking soda.
Add half the dry ingredients and mix on low until combined.
Add the buttermilk and mix on low followed by the remaining flour.
Using a rubber spatula, gently fold in the blueberries and the white chocolate.
Using a large scoop, scoop the batter and drop into the crumb mixture. Gently roll the batter in the crumbs making sure to keep the batter in a round shape. (This might get a bit messy) Place on the prepared baking sheet. Repeat with the remaining batter making a total of 6 muffin tops.
Place the sheet pan with the muffin tops in the freezer for at least 30 minutes.
Bake for 24-25 minutes or until the tops are a golden brown and the top springs back when lightly pressed.
Remove from the oven and place the pan on a rack to cool for 10 minutes.
Remove the muffin tops and place directly on a rack and allow to cool completely.