To make the bisque:

1. Heat 2 tablespoons of olive oil over medium heat in a large heavy pan. Add the prawn heads and shells and cook until the shells have all turned opaque, stirring regularly. This will take around 5 minutes.
2. Add the tomato paste, chopped fennel stalks and half the diced onion. Stir through and cook for 2 minutes. Add the garlic and cook for a further 1 minute.
3. Next add the orange peel, bouquet garni and half the white wine, stir through and cook for 2 minutes. 
4. Add the fish stock, turn down the heat a little and let it simmer very gently for 30 minutes.
5. Remove the bouquet garni and orange peel. Transfer the cooked bisque into a large high-walled mixing bowl. Using an immersion blender, blitz the bisque to break up the prawn shells and vegetables.
6. Using a fine meshed sieve, strain the blitzed bisque into a saucepan. If you are making the risotto straight away, return the saucepan with the bisque to the stove and keep on a low heat to keep it warm.

To make the saffron emulsion:

1. In a glass jar just wide enough to fit your immersion blender add the egg yolk, saffron threads (reserving most of the infused water for the risotto later), 1 garlic clove and lemon juice of half a lemon. Blend with the immersion blender until the ingredients are emulsified.
2. While keeping the blender going, slowly pour the 100 millilitres of olive oil. The emulsion should have the consistency of a runny mayonnaise.
3. The emulsion can be stored in the fridge until ready to serve.

To make the risotto:

1. In a large pan, heat 2 tablespoons of olive oil over medium heat. Add the rest of the diced onion and dices fennel bulb and cook for 2 minutes while stirring. Meanwhile, heat the bisque in a separate saucepan on very low heat to keep warm.
2. Add the rice to the pan with the olive oil and cook for a further 1 minute, continuing to stir.
3. Add the remaining white wine to the rice and stir through. Cook until most of the wine has been absorbed.
4. Now begin adding the bisque to the rice a little at a time. Start with one cup and continue to stir until most of the bisque is absorbed. Then add 1/2 a cup at a time, stirring until absorbed, until all the bisque has been added. During this cooking time, the risotto should be simmering gently, but not boiling. If it begins to bubble too vigorously, turn the heat down a little.
5. At this point, taste a grain of rice to check that is cooked. It should be a little firm but not crunchy. If there is any crunch to it, add a little more water and stir through until it is cooked.
6. Now add the reserved saffron water and stir through.
7. Turn the heat off and add the prawn meat diced into segments and stir through the risotto. The residual heat will be enough to cook the prawns perfectly.
8. The risotto is now read to serve! Serve in flat pasta bowls, top with a drizzle of the saffron emulsion and garnish with fennel fronds.