Cut parchment paper to fully cover two baking sheets.
Put sugar and citrus peel in bowl of food processor, fitted with the steel blade. Process until the peel is finely chopped. Replace the steel blade with the plastic blade, leaving the sugar in the bowl.
Sift flour, baking powder, salt, (and ginger for the lemon-ginger variety) into the food processor. Pulse 5 times. Cut the butter into 1 inch pieces and add to the food processor. Process until the butter is the size of green peas.
In a small bowl, gently whisk the whipping cream, eggs, and vanilla. Add this to the food processor along with one of the following: the ginger nibs, the poppy seeds, the dried cranberries, or the currants, and pulse until the mixture is combined. Don't over-process. Generally I stop after 5 or 10 pulses and put the mixture on a large cutting board to continue gently mixing the dough until all the dry material is incorporated. With your fingertips, pat this mixture together and press or roll gently until it is 3/4 inches thick. It's very important not to overwork the dough or it will be tough! With a 2 3/4-inch round cookie cutter, cut scones, and place on the prepared baking sheets. Pat together the scraps of dough, and cut into scones, but be careful to work the dough as little as possible. If you prefer smaller or larger scones, or even pie-shaped or free-form scones, go ahead.
In a small cup, whisk together the water and remaining egg. Brush each scone with the egg wash. Sprinkle with a little granulated sugar. Place baking sheets on lowest rack and middle rack of oven. After 10 minutes, rotate the pans front to back and interchange the upper and lower pans. Bake another 9-10 minutes until the scones are golden brown, a total of 18-19 minutes. Remove the scones from the oven and put on a cooling rack. Cool for at least 30 minutes before eating. These will stay fresh for 24 hours at room temperature (wrapped tightly in plastic wrap), or you can freeze them for 6 weeks. Please double-wrap in plastic or foil if you are freezing them.