Cream the softened butter with 1/2 cup of granulated sugar until light and fluffy.
Add the vanilla extract and mix in, then beat in the egg until well combined.
In a separate bowl, whisk together the flour, baking powder, and salt.
Gradually add the flour mixture to the wet ingredients and mix until just combined.
Chill the dough for one hour to firm it up.
Preheat your oven to 350°F (180°C) and line baking sheets with parchment paper.
Shape the dough into 1-inch balls and roll them into the remaining granulated sugar.
Using your thumb or the back of a spoon, make an indentation in the center of each ball.
Bake in the preheated oven for 13–16 minutes or until the edges are lightly browned.
Remove from the oven and let them cool on the baking sheet for 5 minutes before transferring to a wire rack.
Spoon raspberry jam into the centers of the cooled cookies.
Prepare the icing by mixing confectioners' sugar, vanilla extract, and water until smooth.
Drizzle the icing over the filled cookies and let it set.
