Preheat toaster oven to 350 F (conventional oven 325 F). Use a foil baking cup or grease a muffin tin. In a small bowl, whisk flour, baking powder and sugar together and whisk until combined. Add vanilla extract and non-dairy milk, and stir until just combined. If too dry, add a few drops of water. Transfer to cup and bake 15-20 minutes, until a toothpick inserted in the center comes out clean. Smear jam over top or mix powdered sugar with a bit of non-dairy milk until it forms a thick, icing paste.