Preheat the oven to 180°C/160°C fan forced. Grease a 3cm-deep, 24cm fluted tart tin with removable base with butter.
Bring the stock just to a simmer in a saucepan over medium heat. Gradually add the polenta in a thin, steady stream, stirring constantly until combined. Reduce heat to medium-low and cook, stirring, for 10-15 minutes or until thickened. Remove from heat. Stir in 3⁄4 cup of the parmesan and 1 of the eggs until well combined. Season. Press into the prepared tart tin to line the base and side. Bake for 20 minutes or until light golden and set.
Meanwhile, cut each zucchini in half crossways. Working with 1 piece at a time, use a spiraliser to cut the zucchini into noodles. (Alternatively, peel into ribbons, then use a knife to cut into strips). Twirl 1 portion around your fingers to make an 8cm nest. Place on a chopping board. Repeat with remaining zucchini to make 6 nests.
Combine the ricotta, goat’s cheese, 3/4 cup of the remaining parmesan and the remaining egg in a bowl. Season well. Spread into case. Top with zucchini nests. Place a bocconcini in centre of each nest. Sprinkle with the remaining parmesan.
Place the tart on a baking tray. Arrange tomatoes on the tray around the tart. Bake for 20-25 minutes or until cheese melts and tomatoes are just starting to collapse. Top tart with tomatoes. Sprinkle with parsley.