In a bowl, mix flour, baking powder, sugar, and salt, until completely combined, set aside

Melt unsalted butter in microwave at 30 seconds

On a separate bowl, beat eggs and vanilla essence together, then pour mixture into dry ingredients, along with melted butter

Mix mixture into a dough

Spoon a tsp each of dough and fill up the mold. Cook cookies for 2-3 minutes on each side, until golden brown (as walnuts can be light brown to dark brown, so can your cookies be, if you want them to be similar to walnut color!)

Cool completely before filling, and cut off excess to more resemble the shape of a walnut

Spoon caramel spread on each cavities, then sandwich them together