In the bowl of a stand mixer fitted with the paddle attachment, beat the cream cheese and butter together until they are combined. Then add the granulated sugar and continue beating on medium-high speed until light and fluffy (2-3 minutes.
Reduce the speed to medium and add the egg yolk and vanilla, continuing to beat until smooth.
Sift the flour, baking powder, and salt together in a separate bowl. Then add it them to your mixer, combining everything together on low speed until a dough comes together and flour is just combined. Cover and transfer this dough to the fridge to chill for 20 minutes.
When you're ready to bake, preheat the oven to 350°F/180°C and line two cookie sheets with parchment paper.
Roll the dough into roughly 1" balls (I measured out each into 25 gram portions). Use your thumb or bottom of a small spoon to press into the middle of each ball, roughly ½ inch deep. Add a small spoonful of jam to fill the well. Space the cookies 2" apart on the sheets.
Bake for 14-15 minutes, or until cookies are puffed up, set, and a little golden along the edges. Let them cool completely.
To make the optional icing drizzle on top, whisk together the powdered sugar, milk, vanilla, and salt until smooth. Drizzle over the cookies and enjoy!