Combine flour, polenta, sugar, rind, cream of tartar, baking soda and salt in a bowl. Combine egg, cream, vanilla and butter in a jug and whisk to combine. Pour onto to the dry mixture and mix until just combined.
Spoon into 24 hole mini-muffin pan, filling no more than halfway. Bake into golden and puffed, about 10-12 minutes, or until a skewer comes out clean. Cool for a few minutes, then turn out and cool on a wire rack.
