Preheat oven to 325°F. Grease the wells of a tartlette pan and dust with flour. Place pan on a baking sheet.
In a medium bowl, whisk together the flour, baking powder and soda, and salt.
In a small bowl, whisk together the sugar, egg, and butter until thoroughly combined.
Add the milk and vanilla to the egg mixture and stir to combine. Whisk the liquid into the flour mixture just until all the flour is incorporated. Do not over mix
Divide the batter amongst the prepared tartlette wells. Gently press a heart into the center of the batter**
Bake for 22-24 minutes, until the center is set.
Allow to cool in the pan for 10 minutes. Remove the cakelettes from the pan, including the tartlette base and cool completely on a cooling rack.
Notes
*Microwave the butter for 10-15 seconds until most is melted but some solid butter remains. Stir to melt the remaining solid butter. Allow to cool until the butter reaches a stiffer consistency, resembling the consistency of mustard.**No need to submerge the heart. Only about 1/3 of the heart needs to be in the batter. Storage Store in an airtight container for up to 2 days