For the goats' buttermilk sorbet, place all of the sorbet ingredients into a food processor and blend until smooth. Pass the mixture through a fine sieve into a clean freezer-safe bowl. Place into the freezer, removing to whisk every 15 minutes, to break up the ice crystals, until the mixture is frozen. (Alternatively, you can churn the mixture in an ice cream machine according to the manufacturer's instructions.)
For the puff pastry cases, cut the pastry into four 60g/2¼oz pieces and roll out into 6cm/2½in x 8cm/3in rectangles (you can use the left-over pastry for another dish). Trim theedges, then place the rectangles onto a non-stick baking tray and place into the fridge to chill for 30 minutes.
Remove the tray from the fridge and brush each piece of pastry with a little egg wash around the edge of the pastry. Using a sharp knife, score a smaller concentric rectangle inside the pastries to create a 1cm/½in border.
For the tart filling, peel and cut the red onions in half across the root of the onion and then slice across finely into semicircles.
Place the butter and sugar into a non-reactive pan over a medium heat and cook until melted and turning light brown.
Add the red onions and mix well.
Add the red wine, bay leaf, star anise and vinegar and bring to the boil. Reduce the heat and simmer for 20 minutes, until most of the wine and vinegar has reduced and the red onion mixture looks like a marmalade. Remove from the heat and leave to cool. Remove the bay leaf and star anise.
Preheat the oven to 220C/425F/Gas 7.
When the red onion marmalade has cooled, place a small teaspoon of the red onion marmalade into the middle of each raw puff pastry rectangle.
Transfer to the oven to bake for 15-20 minutes, or until the pastry is golden-brown in colour and crisp on the bottom.
For the wild garlic and basil dressing, place the wild garlic leaves, basil and olive oil into a food processor and blend until smooth. Season, to taste, with salt and freshly ground black pepper and refrigerate until ready to serve.
For the wood pigeon, season the pigeon breasts well with salt and freshly ground black pepper. Heat the oil in a frying pan and add the pigeon breasts skin-side down. Fry for five minutes, then turn the breasts over and fry for two minutes, or until cooked to your liking. Remove from the heat and leave to rest for 2-3 minutes.
When ready to serve, spoon the frozen sorbet into shot glasses or serve on mini ladles.
To serve, place the rocket into a bowl. Drizzle with some of the wild garlic dressing and mix well. Place the tarts onto serving plates. Slice the warmed pigeon breasts and place on top of each tart. Place a handful of the dressed rocket salad alongside the tart with a spoonful of wild garlic dressing alongside. Serve each with a shot glass or ladle of sorbet.