Preheat the oven to 350 degrees F. Line a heavy large baking sheet with parchment paper.
Whisk the flour and baking powder in a medium bowl to blend. Using an electric mixer, beat the sugar, butter, lemon zest, and salt in a large bowl to blend. Beat in the eggs 1 at a time. Add the flour mixture and beat just until blended. Stir in the pistachios and cranberries.
Form the dough into a 13-inch-long, 3-inch-wide log on the prepared baking sheet. Bake until light golden, about 40 minutes. Cool for 30 minutes.
Place the log on the cutting board. Using a sharp serrated knife, cut the log on a diagonal into ½- to ¾-inch-thick slices. Arrange the biscotti cut side down on the baking sheet. Bake the biscotti until they are pale golden, about 20 minutes. Transfer the biscotti to a rack and cool completely.
Stir the chocolate in a bowl set over a saucepan of simmering water until the chocolate melts. Dip half of the biscotti into the melted chocolate. Gently shake off the excess chocolate. Place the biscotti on the baking sheet for the chocolate to set. Sprinkle with the sugar crystals. Refrigerate until the chocolate is firm, about 35 minutes.
As you dip the biscotti into the melted chocolate, you can also dip them into crushed pistachios if you like.
The biscotti can be made ahead. Store them in an airtight container up to 4 days, or wrap them in foil and freeze in re-sealable plastic bags up to 3 weeks
Melt the butter in a medium skillet over medium-high heat. Add the onion, season with salt and cook until golden brown, 4 to 6 minutes; set aside. Combine 1/2 cup breadcrumbs and the milk in a bowl; set aside until the milk is absorbed, 1 to 2 minutes. Stir the sherry and mustard powder in a large bowl until dissolved, then beat in 1 egg. Add the soaked breadcrumbs, the browned onion, the pork, turkey, honey, allspice, 2 teaspoons salt, and pepper to taste. Gently mix with your hands until combined. Dampen your hands; form the mixture into 36 small meatballs, about 1 tablespoon each. Put on a parchment paper-lined baking sheet, cover with plastic wrap and refrigerate at least 4 hours or overnight. Put the remaining 1 cup breadcrumbs in a shallow dish. Whisk the remaining 2 eggs and 2 tablespoons water in a bowl. Dip each meatball in egg, letting the excess drip off, then roll in the breadcrumbs; return to the baking sheet. Heat about 1 1/2 inches vegetable oil in a large saucepan over medium-high heat until a deep-fry thermometer registers 325 degrees F. Working in batches, fry the meatballs, gently stirring with a slotted spoon, until golden and cooked through, 3 to 4 minutes. Transfer to a paper towel-lined plate and season with salt. Let stand 10 minutes. Fold the lingonberry preserves into the sour cream and top with the dill. Skewer each meatball with a pickled cucumber slice and serve with the lingonberry cream.