Preheat the oven to 350°F.

In a mixing bowl, cream the butter and sugar together until light and fluffy.

Add the egg yolk and mix until well combined.

Gradually add the flour, mixing until a soft dough forms.

Press the dough into 8 greased tartlet tins and prick the bottoms with a fork.

Bake the tartlet shells for 10-15 minutes, or until lightly golden. Allow to cool.

In a saucepan, combine the sweetened condensed milk, butter, golden syrup, and vanilla extract. Cook over low heat, stirring constantly, until the mixture thickens and turns a caramel color (about 10-15 minutes).

Pour the caramel mixture into the cooled tartlet shells and allow to cool completely.

Serve with a dollop of whipped cream.