Method

• 1.
  For the prawn stock, heat oil in a large heavy-based saucepan over high heat. Add prawn heads and shells, and cook, stirring and breaking them up, for 5-6 minutes until shells start to brown. Stir in tomato paste and cook, stirring, for 30 seconds to 1 minute until tomato paste starts to stick to the base of the pan. Pour in 4 cups (1L) water, scraping the bottom of the pan with a wooden spoon. Bring to the boil, reduce heat to low and simmer for 30-35 minutes until reduced by half. You should have about 500ml stock. Strain through a fine sieve and reserve. Discard solids.
• 2.
  Meanwhile, bring a large saucepan three-quarters full with water to the boil. Blanch the chicory for 30 seconds or until just wilted. Refresh in iced water, drain well.
• 3.
  Return pan to heat and fill three-quarters full of salted water. Bring water to the boil, add spaghetti and cook according to packet instructions. Drain and set aside.
• 4.
  Heat half the butter in a large frypan over high heat. When butter begins to foam, add eschalot, garlic, tomato and dried chilli, if using. Cook, stirring, for 4-5 minutes until eschalot begins to soften. Stir in prawn and cook for 1-2 minutes until prawn begins to change colour. Add stock and remaining 45g butter. Bring to the boil and simmer for 6-7 minutes until butter and stock have emulsified and thickened slightly.
• 5.
  Add the spaghetti, chicory, lemon zest and juice to the sauce and toss to combine. If your pasta soaks up the sauce quickly and is a little dry, add some water. Season to taste. Serve immediately.