Step 1 Preheat oven to 200ºC. Place tomatoes and garlic on a baking tray and spray with oil. Roast for 20 minutes, until tomatoes soften.
Step 2 Meanwhile, flatten chicken breasts using a rolling pin or mallet. Spray a non-stick pan with oil and cook chicken over medium heat for 2 minutes per side, until cooked through. Slice into thin strips, cover and keep warm.
Step 3 When cool, peel garlic and place into a blender with three-quarters of the tomatoes. Process until smooth. Pour mixture into a small saucepan. Add evaporated milk, sugar, pepper and 3 tablespoons of basil, and heat over low heat until warmed.
Step 4 Meanwhile, cook spaghetti according to packet directions.
Step 5 Drain spaghetti and divide between serving plates. Top with sauce and chicken. Garnish with remaining basil and roasted tomatoes.