Preheat your oven to 350°F. In the bowl of a stand mixer, cream the butter and sugar together until soft and fluffy, about 5 minutes. Meanwhile, whisk together the flour, baking powder, and salt in another bowl until well incorporated. Beat the egg and vanilla into the butter mixture until combined, then slowly add the dry ingredients with the mixer on the lowest setting until a dough forms.
Scoop tablespoonfuls of dough out and roll into a ball with your hands. Place the dough balls on a greased baking sheet about 1 1/2 inches apart from each other. Carefully make an indentation in each dough ball with your thumb, deep enough to form a well without breaking the bottom.
Stir your cooled jelly to roughen the texture up so it's easily spoonable. Carefully spoon enough jelly to fill each well to the top. Bake the cookies for 13-15 minutes, until they start to turn golden at the edges and bottom. The tops will stay light, so don't worry. Allow to cool on a baking rack, and then drizzle with a fork dipped into the melted chocolate.