• Line a cupcake or muffin pan with 12 paper liners (see note 2)
• Preheat the oven to 356° F / 180° C (160° C fan)
• Add butter to a small pot and heat on the stove until just melted. Alternatively, you can melt it in the microwave using a microwave-safe bowl.
• Pour the warm melted butter into a large bowl. Add sugar and vanilla extract and whisk to combine.
• Sift the flour, baking powder, and salt into the butter mixture and use a spatula to combine. Gather the dough with your hands; it will feel soft and slightly crumbly.
• Press 2 packed teaspoons of dough into the bottom of each muffin liner, reserving about ¾ cup (about 80g) of dough for the crumb topping.
• Spread 1 teaspoon of jam evenly over each cookie. (See note 3)
• Use your fingers to crumble the reserved dough in the bowl and sprinkle it either over the jam or around its edges. (See note 4)
• Bake for 15-20 minutes until golden brown. Remove the pan from the oven and let the cookies cool in the pan for 10 minutes, so they are firm enough to transfer to a cooling rack without breaking.

Storing

• Storing baked cookies: Store baked and cooled cookies in an airtight container at room temperature for up to 5 days, or freeze them for up to 1 month.
• You can prepare the dough in advance if you like. Refrigerate it for up to 3 days or freeze it for up to 2 weeks.