In a cup, stir cornstarch and vanilla in 2-3 tbsp of plant-based milk to dissolve. Bring the remaining milk to the boil in a pot, add the cornstarch mixture and bring to the boil again, while stirring constantly. Stir in vegan butter and sugar, so you have a creamy custard, then allow to cool slightly. Blend the soy quark with soy flour until creamy and fold in the pudding. Mix until creamy and once cooled, fill into the prepared shortcrust.