1. Butter an 8 1/2-inch cake or springform pan; set aside. Sift 2 teaspoons ground ginger and 1/2 teaspoon ground white pepper with the flour and salt into a small bowl; set aside. Place butter in bowl of electric mixer fitted with paddle attachment. Cream until fluffy, 3 to 5 minutes. Add sugar, and continue to beat until very light in color and fluffy, occasionally scraping down the sides of the bowl with a spatula, about 2 minutes more. Add vanilla, if using. Add 1/2 cup finely chopped candied ginger to the creamed butter-and-sugar mixture before adding the flour mixture. Add flour mixture, and combine on low speed, scraping with spatula if necessary, until flour is just incorporated and dough sticks together when squeezed with fingers.

2. Pat the dough into pan or pans. Sprinkle 1/4 cup chopped ginger and 1 tablespoon crystal sugar over each pan before baking.

3. Heat oven to 325 degrees. Bake until firm and just starting to color, 30 to 40 minutes.