Preheat oven to 425°F (220°C). Line a muffin pan with liners.
First make the crumble topping by mixing together all the crumble ingredients (flour, sugar, butter) then mix with a fork until crumbly. Set this aside.
In a bowl, rub the lemon zest into the sugar using your fingers to release the oils. Then add the eggs and whisk until well combined.
Add the rest of the wet ingredients: melted butter, oil, lemon juice, yogurt, milk, and vanilla. Whisk this until smooth.
In a separate bowl, sift together the dry ingredients: flour, baking powder, and salt.
Gently fold the dry ingredients into the wet until just combined. Do not overmix at this point. Next, fold in the blueberries.
Divide batter evenly between 12 muffin cups. Then top generously with the crumble.
Bake at 425°F (220°C) for 5 minutes, then reduce the temperature to 350°F (180°C) without opening the oven door, and bake for another 15–18 minutes until golden and a toothpick comes out clean.
Let cool slightly, then drizzle with lemon glaze,