Whisk egg white and lemon juice with the whisk of the hand mixer until thick and creamy white. Add 150 g sugar and continue beating until the sugar has dissolved and the beaten egg whites are shiny white.
Line 2 baking trays with baking paper. Place 6 meringue piles on each baking tray with a tablespoon. Press down lightly. Bake in the preheated oven (electric cooker: 100 °C/ convection oven: 75 °C/ gas: see manufacturer) one sheet at a time for about 1 1/4 hours. Remove from the oven, place on a cake rack and allow to cool.
In the meantime wash the plums, cut them in half and remove the stones. Bring port wine, 75 g sugar, 1 packet of vanillin sugar, 250 ml water and plums to the boil. Simmer for 3-4 minutes. Stir starch and 3-4 tbsp water until smooth. Stir into the boiling liquid, bring to the boil and simmer for about 1 minute. Stir several times. Remove from the heat and allow to cool.
Whip the cream with the whisks of the hand mixer until semi-stiff, while pouring in 1 sachet of vanillin sugar. Carefully remove Pavlova from the baking paper. Arrange on a large plate, spread the cream as a blob and drizzle some plum jelly over it. Decorate with mint. Add the rest of the plums.