For the lemon yoghurt topping, whisk together the yoghurt, lemon curd, honey, and vanilla and set aside at room temperature.
For the fruit salad, carefully toss together the strawberries, raspberries, blueberries, sugar, and limoncello. Allow them to stand at room temperature for about 5 minutes to let the berries macerate with the sugar and liqueur. Gently fold the banana into the mixture.
Serve bowls of fruit with a dollop of lemon yoghurt on top. Top each with a sprig of fresh mint.