Preheat oven to 350°F (177°C). Line a cookie sheet with parchment paper.
In a mixing bowl, beat the butter and icing sugar until smooth and fluffy.
Mix in vanilla extract, then beat in the egg until fully combined.
Add flour and a pinch of salt. Mix just until a soft dough forms.
If needed, chill dough for 20–30 minutes for easier shaping.
Roll dough into small balls and place on the cookie sheet. Press the center of each ball to make a well.
Spoon strawberry jam into each center.
Bake 10–12 minutes, until edges are lightly golden and jam looks set.
Cool on the pan for 5 minutes, then transfer to a wire rack to cool completely.
