Preheat oven to 375 degrees F. In the bowl of an electric mixer, cream together butter and sugar. Add cheeses, herb seasoning, baking powder, the ½ teaspoon of salt and pepper and continue beating until creamy. Add eggs one at a time, beating well after each addition. Add flour gradually and continue beating until dough is well combined. Finally, carefully mix in sun-dried tomatoes and walnuts. Divide it into three pieces (about 10-12 ounces each), and shape each piece into a roll about 8 inches long. Space the three rolls evenly apart on a parchment-lined cookie sheet and shape each into a rectangle about 2-½ inches wide and 1 inch thick. Brush the top of each rectangle with water and sprinkle with the Kosher or coarse sea salt. Bake the rectangles 20 to 25 minutes, or until slightly brown at the edges. Remove them from the oven, and cool for about 30 minutes. Lower the oven temperature to 300 degrees F. Using a serrated knife, carefully cut each rectangle diagonally into ⅝ to ¾ -inch wide slices. Place slices on their sides (cut sides up and down) to a parchment-lined cookie sheet. Bake the sliced biscotti in the 300 degree F oven for 20 minutes. Remove from the oven, turn them over, and bake for another 20 minutes, or until dry and beginning to brown. Remove them from the oven and transfer to a cooling rack. * You may substitute finely shredded sharp cheddar if necessary.