Preheat the oven to 180C/350F degrees
Whisk the butter and erythritol until blended.
Add the vanilla extract and the eggs, one at a time and continue to whisk.
Add the coconut flour, baking powder, salt and coconut milk and whisk until smooth.
If the mixture is too thick, add a tablespoon or two of water until the consistency is smooth.
Line a muffin tin with 9 cupcake cases.
Spoon a small amount of the cupcake mixture into the cases and spread to make a base.
Place the sponge hearts in the middle of each cupcake case, upright.
Gently spoon the cupcake mixture around the heart, then cover the top of it.
Bake for 20-25 minutes until the cupcakes are firm
Remove from the oven and set aside to cool