• Preheat the oven to 350 F (175 C).
• In a small bowl, combine the white chocolate and butter and melt it in the microwave for 10-20 seconds. Mix well.
• In a large bowl, beat the eggs with the sugar and vanilla extract for 2-3 minutes until a foamy mixture is obtained. Add the melted white chocolate, flour, baking powder and salt and mix well.
• In a small bowl, mix the blueberries with the flour (this helps them not sink to the bottom). Add the blueberries to the batter and gently fold.
• Divide the batter into the 12 cups in the muffin pan.

Crumble:

• In a bowl, combine the flour, melted butter, sugar, lemon zest and salt. Sprinkle a little crumble on top of each muffin.
• Bake for 20-25 minutes until the muffins are golden on top and completely firm.