Hippocrates, the father of medicine, is said to have first suggested the healing power of food, when in 431BC he said: "Let food be thy medicine and medicine be thy food." In the past decade, many studies have shown a relationship between what we eat and brain function. Flavanols have been associated with a decreased risk of dementia, according to the American Heart Association. Research by the Alzheimer's Association in 2009 showed that eating a "heart healthy" diet and participation in moderate physical activity may help preserve our memory and thinking abilities as we age. It suggested that whole grains, vegetables, low-fat dairy foods and nuts may offer benefits for cognition in later life. Food - or, more specifically, cooking - can help develop our imagination, which is constantly under threat of being repressed, by the "common sense" of the communities in which we live. I spent an afternoon with chef Pietro Leemann at Ristorante Joia in Milan, Italy. He believes in the power of ideas: "Most chefs make dishes that are a combination of ingredients. But my food is the outcome of a creative artistic process." As he speaks, Leemann places a dome-shaped crispy leaf of cabbage to conceal a vegetable terrine. He calls the dish "The Navel of the Planet". The cabbage dome is a symbol for the world and the need for a green solution to protect it. Joia was the first vegetarian restaurant in Europe to be awarded a Michelin star. The menu lists dishes such as Wild, Travel Notes, Serendipity in the Garden of My Dreams, and The Phoenix's Dream. "I look at nature, and I transform it in order to understand it and represent its essence," says Leemann. "I love to do so by using a tantalising and playful approach." Leemann believes cooking is a vehicle for creating relationships between ourselves and nature. When the liaison is playful, it works better, like in human relationships. Leemann presents a dish called Fabrizio Thought About Me, which is named after Fabrizio Marino, Joia's sous chef. Fabrizio Thought About Me Serves 4 For the terrine 100 grams carrots 100 grams fennel 50 grams leek 100 grams red cabbage 50 grams celery 2 grams orange zest 30 grams butter 5 grams chopped rosemary 200ml water 1 gram agar agar powder Salt Cut vegetables into small pieces, lightly season with salt and sweat over a very low heat, covered with a lid, until golden brown. Puree in a food processor with the butter, rosemary and orange zest. Bring water to the boil with the agar agar, reduce to 50ml, stirring constantly with a whisk. Add to the vegetables. Pour the mixture into an aluminium mould and allow to cool until it sets. Keep in the refrigerator; when ready to serve, cut into 4cm circles. For the pickled pears 2 small pears 200ml water 50 grams sugar 2 grams turmeric 25ml apple vinegar Half gram agar agar powder Peel the pears and cook in water with the sugar and vinegar until soft. Cut each pear into four pieces. Divide the syrup in two. Mix the turmeric into one half, add the pears and set in the refrigerator. Mix the other half with the agar agar, boil and reduce to 50ml. For the raspberry sauce Put the pear jelly into 4cm diameter moulds, pour the agar agar mix on top and leave to set in the refrigerator. 200 grams fresh raspberries 20 grams sugar 50ml apple vinegar Pour apple vinegar and sugar into a pan and bring to the boil. Add the raspberries and reduce for 10 minutes then strain through a sieve. For the green sauce 120 grams parsley 100ml extra virgin olive oil 1 tbsp capers 1 tbsp lemon juice 3 anchovy fillets 2 cloves of garlic 2 grams black sesame seeds Chop the parsley, capers, anchovy fillets and garlic. Add the lemon juice and olive oil and stir until thick. Use one terrine circle and one pickled pear circle for the eyes. Draw a smile with the green sauce and the eyebrow with the raspberry sauce.