1/2 bunch Italian parsley, cleaned and dried
1/2 bunch fresh dill, cleaned and dried
1/2 bunch fresh watercress, cleaned and dried
1/2 cup drained cooked fresh spinach, all liquid squeezed out
2 scallions (green onions) tender greens included, sliced thin
2 cups mayonnaise
1 cup sour cream
to taste salt and ground black pepper

In the bowl of a food processor, fitted with a steel blade, chop finely parsley, dill and watercress. Transfer to a mixing bowl.
Process spinach in the same way and add to herb mixture. Add scallions, mayonnaise and sour cream. Season to taste with salt and ground black pepper.
Refrigerate until ready to use.