3garlic heads60 ml (¼ cup)olive oil20 gmbutter1onion, finely chopped1.5 litres (6 cups)chicken stock1.2 kgparsnips (about 6), cores removed, coarsely chopped250 ml (1 cup)pouring cream2 tbsplemon juice, or to tasteTo serve:sage flowers, optionalLemon and sage butter80 gmcold butter, coarsely chopped¼ cup (loosely packed)sage leavesJuiceof 1 lemon
Preheat oven to 180C. Place garlic on a large sheet of foil, drizzle with 20ml olive oil and wrap to enclose. Place on an oven tray and roast until very tender (30-35 minutes). Set aside to cool. When cool enough to handle, squeeze garlic from skin (discard skin) and set aside.
Meanwhile, heat butter and remaining olive oil in a large saucepan over medium heat, add onion and stir occasionally until tender (6-8 minutes). Add stock and parsnip, bring to the boil, cover and simmer until parsnip is very tender (45 minutes-1 hour). Add garlic and cream and purée with a hand-held blender until smooth (add a little water if necessary to reach required consistency). Season to taste with sea salt, freshly ground pepper and lemon juice, set aside, keep warm.
Meanwhile, for lemon and sage butter, heat butter in a frying pan over medium heat until foaming. Add sage and fry until crisp (1-2 minutes), quickly transfer leaves with a slotted spoon to a plate lined with absorbent paper, add lemon juice to pan, remove from heat.
Serve soup hot, scattered with sage leaves and flowers and drizzled with lemon butter.