Pre-heat an oven to 190 degrees/gas 5. Put the empty prawn shells in a roasting tray and roast for 40 minutes. Remove the shells from the roasting tray and scoop them into a pot. Pour two litres of water on top and bring it to the boil. Turn down to a simmer and cook the stock for 40 minutes.

When you’ve five minutes cooking time left for the prawn stock, add the butter to a separate heavy pot. When it is melted, whisk in the tomato puree, then the sherry, followed by the flour.

Turn the heat down very low and continue to mix well for five minutes. Now strain in the prawn stock, and whisk until smooth. Turn the heat up, but do not boil. Whisk in the cream, adjust the seasoning and simmer very gently till you have a sauce consistency.

Slice the potatoes into even slices. Cover them with cold water and add two teaspoons of salt. Bring to the boil, simmer until cooked. Strain and set aside, covered with foil.

Add all the prawn poaching liquor ingredients to a pot. Bring to the boil then immediately turn down to a simmer.

Separately, bring one litre of water to the boil and add three teaspoons of salt (this is for the peas).

For the saffron potatoes, melt the butter with the saffron in a heavy frying pan. Season the potatoes and then saute them in the butter and saffron, without browning them.

Drop the raw prawns into the cooking liquor for three to four minutes, then remove them with a slotted spoon.

Drop the peas into the boiling salted water for 25 seconds, then remove them and season lightly.

To serve: Split the potatoes between six plates and add eight prawns to each. Scatter a spoonful of garden peas on each plate and drizzle two to three tablespoons of prawn bisque over each portion.