Place unpeeled potatoes and carrots in a pot and cover them with water. Bring to a boil and cook about 20 minutes until tender but not too soft. (Put the frozen peas in a colander and place the cooked potatoes on top to assist in the thawing process.) Peel and dice carrots and potatoes once cooled and place in a large bowl along with the peas, diced eggs, gherkins and spam. Season with salt. Add equal parts of sour cream and mayonnaise a little at a time until desired wetness. Serve chilled.