Whisk yeast with warm water and 1 tablespoon of Natvia in a small bowl until yeast is dissolved. Set aside in a warm place for 5 minutes or until mixture is frothy.
Combine flour, mixed spice, cream of tartar, bicarb soda, a pinch of salt and the remaining ¼ cup Natvia in a large bowl. Make a well.
Add yeast mixture, butter, almond milk, egg and vanilla. Mix until a soft, sticky dough forms. Turn out onto a lightly floured surface. Knead for 2 minutes to form a smooth ball.
Place the dough in a lightly oiled bowl and cover with a tea towel. Leave in a warm area for about an hour to prove.
Line two Baking trays with baking paper, take pieces of dough (around a tablespoon) and roll into balls, place on the prepared trays.
Make the flour paste: Mix flour and water in a small bowl until smooth, adding a little more water if too thick. Spoon into a disposable piping bag and pipe a cross onto the top of each dough ball. Stand for 20 minutes.
Place the extra Natvia in a bowl with the cinnamon. Fill the other disposable piping bag with either Nutvia, Natvia Strawberry or Raspberry Jam.
Pour oil into a deep frying pan or small pot until 1/3 full, heat over a medium heat. Cook doughnuts in batches for 1-2 minutes or until golden.
Using a slotted spoon, transfer to a tray lined with paper towel to drain for 10 seconds. Pierce doughnuts with a knife or skewer. Fill with Nutvia or Jam. Toss the filled doughnuts in the Natvia, cinnamon mix to coat. Place on a plate.