For the parsnip and vanilla soup, melt the butter in a saucepan over a low to medium heat, add the onion and garlic and fry gently until softened, but not coloured.
Add the parsnips to the pan and continue to fry until the parsnip cubes start to break down and soften.
Add the vanilla pod, milk and stock to the pan and bring the mixture to the boil. Reduce the heat and simmer until the parsnip is tender, about 8-10 minutes.
Transfer the mixture to a food processor and blend until smooth and silky. Season, to taste, with salt. Pass the mixture through a fine sieve into a saucepan and keep warm.
For the saffron-poached quince, squeeze the lemon juice into a jug. Add the cold water (this is called acidulated water).
Peel the quince and, using a melon baller, scoop the quince into balls. Place the quince balls into the acidulated water to prevent them from going brown.
Place the sugar, water and saffron into a saucepan and bring to the boil. Drain the quince balls and add them to the pan. Simmer gently until tender, about 8-10 minutes. Remove the pan from the heat and set the quince aside in the saffron sugar syrup to cool.
For the scallops, cut the scallops in half to create two semi-circular pieces of scallop. Lightly season the scallops with salt.
Heat a heavy-based, non-reactive, non-stick pan over a medium heat until warm, but not hot. Add the light olive oil to the pan.
Place the scallops into the pan, cut-sides down. Increase the heat to high and fry the scallops for one minute, or until lightly coloured.
Turn the scallops over, turn off the heat, then add the butter to the pan. Cut the lemon in half and squeeze the juice from one of the lemon halves into the pan. Reserve the remaining lemon.
When the scallops are just cooked through on the residual heat of the pan, remove them from the pan and set aside to rest for one minute.
Meanwhile, for the tarragon crisps, cover a plate tightly in cling film. Lightly smear a little groundnut oil over the surface of the cling film.
Pick 12 large sprigs of tarragon from the bunch and lay them flat onto the cling film.
Drizzle a little groundnut oil over the tarragon sprigs and season lightly with salt.
Place in the microwave and cook for one minute on high. Remove from the microwave and set aside to cool.
To serve, drain the quince balls. Place 3 scallop halves, 7 quince balls and 3 tarragon crisps into each of four warmed serving bowls. Ladle the soup around the contents of the bowl and serve immediately.