For the gnocchi mix well the boiled and mashed potatoes, refined flour, salt, crushed black pepper and egg yolk, to knead a soft dough. Roll the dough into a rope like shape and cut small portions for the gnocchi. Make balls from some of the cut portions, flatten slightly and make a very small cavity in the centre of each gnocchi. Dust flour during the shaping process. Flatten the remaining portions into several rope like pieces. Boil water in a deep pot and allow it to simmer on a low flame. Add some basil leaves to it and place the gnocchi in the hot water. The gnocchi will be cooked when they float on the surface of the water. Set aside and drizzle some olive oil. Blend the basil leaves, garlic, Parmesan cheese, cashewnuts, olive oil. Season with salt and black pepper powder. Mix well. Your pesto is ready. In a bowl, mix the pesto, gnocchi, chopped tomatoes and basil leaves. Gently toss the salad. Garnish with Parmesan cheese and serve.