Preheat oven to 350°F
In a bowl with a handheld mixer add the softened butter and sugar until you form a dough.
Add the egg yolk and vanilla extract and mix on low until the egg is fully combined.
Add the flour and mix until a shaggy dough forms.
Finish forming the dough with your hands and use a cookie scoop to divide the dough into small size balls (about the size of a lime).
Place the cookie balls in a baking sheet and using the back of a spoon, create an indentation in the center.
Bake the dough for 12 minutes. Half way through baking, remove the sheet from the oven and use the spoon again to make sure the indentations are deep enough.
Finsih baking and transfer to a cooling rack.
Add about 1 teaspoon of jam in the center of the cookies and allow them to set for 10 minutes. Decorate with sprinkles and enjoy.