• Preheat the oven to 350F.
• Drop paper liners into the holes of a a 12-hole muffin pan.

Mix the batter

• Sift the flour, baking powder and salt into a bowl.
• In a large mixing bowl, beat the butter and vanilla sugar until light and fluffy. DO NOT overmix: you will know you have overmixed if the butter solids separate from the fat.
• Add the eggs, one at a time, beating after each addition and making sure that the egg is fully incorporated in the mixture before adding the next one.
• Add the flour and milk in batches. Add a third of the flour first, mix; add half of the milk, mix; add the next third of the flour, mix; then the remaining milk and, finally, the rest of the flour.
• Use an ice cream scoop to divide evenly among the holes of the pan.

Make the streusel topping

• Stir the sugar and flour.
• Add the butter and rub with your fingers until coarse crumbs are formed.
• Sprinkle the crumbs evenly among the 12 cupcakes.

Bake

• Place the muffin pan on a baking tray.
• Bake the cupcakes at 350F for 20 to 25 minutes.
• These vanilla streusel cupcakes are best served warm.