Mix 40g plain flour, 65g sugar, and 30g cold butter in a bowl
Rub in the butter until a crumbly texture is achieved
Chill the streusel in the fridge until ready to use
In a separate bowl, combine 4 medium eggs, 150g sugar, 100ml oil, 160ml milk, 120ml buttermilk or natural yogurt, 90ml whipping or heavy cream, and 1 tsp vanilla essence
Mix in 370g plain flour, 2 tsp baking powder, and ½ tsp salt
Fold in 200g blueberries
Divide batter into 12 large tulip muffin cases
Top with prepared streusel
Bake at 210°C in a conventional oven for 5 minutes
Reduce temperature to 190°C and bake for 20 minutes
Cool and enjoy
