Heat the oven to 200 degree C. Cut the top third off the garlic head, place in some foil, season and drizzle with 1 tbsp olive oil. Crunch the foil around it and roast for 45 minutes. Set it aside.
Heat the stock in a low rolling simmer. Fry the oinion and Turnip greens in butter until soft. Add the rice and cook for a couple of minutes until slightly translucent.
Keeping the heat on medium, pour in the white wine and keep stirring until it is absorbed.
Stir in the stock about a ladle at a time and each time wait for the rice to absorbe the liquid before adding more. Squeeze the roasted garlic into the rice about halfway through.
Continue with the rest of the stock. When the rice is cooked but has a slight firmness, remove from the heat. Beat in the lemon zest.