Cut the Tsoureki into slices and then into cubes. In a bowl, whisk together the eggs, milk, heavy cream, sugar, and vanilla extract. Butter a pan with dimensions 23x30cm and place the Tsoureki cubes in it. Pour the liquid mixture over the bread cubes and set it aside for half an hour to allow the bread to soak up the liquid. Add the berries and mix. Sprinkle with brown sugar and bake at 180°C for 30-40 minutes or until the surface of the pudding is golden brown. When ready to serve, sprinkle with powdered sugar and garnish with extra berries and mint leaves.