Thoroughly wash the clams. Chop the shallots into a fine dice and cook in the butter until soft, then add the chopped garlic and 1 glass of the white wine and reduce slightly. This can be done up to 2 to 3 days in advance, cooled and kept in a sealed jar.
Place a large pan on the gas and allow it to heat up, adding the clams and the remaining white wine. When they all start to open add the cooked spaghetti to the same pan. Then add the double cream and the cooked shallot mixture.
After 2 to 3 minutes when everything is warmed through, check the seasoning and adjust if necessary and add some of the chopped parsley. Serve in hot bowls and finish with the rest of the chopped parsley.