Method:
Preheat the oven to 350°F. Butter a 9x13-inch baking pan and line the bottom with parchment paper, letting paper extend about 1 inch over the short ends of the pan. Butter the paper and flour the pan.
Sift together flour, baking powder, baking soda, ground ginger, cinnamon, allspice and nutmeg, and set aside. With an electric mixer, beat butter or oil and brown sugar together until light. Beat in molasses. Beat in eggs one at a time. In 3 additions, stir in flour mixture, alternating with additions of milk, beginning and ending with flour. Stir in 2 tablespoons of crystallized ginger.
Scrape batter into the prepared pan and level the top. Sprinkle the top with the remaining 2 tablespoons crystallized ginger. Bake until a toothpick inserted in center comes out clean, 25 to 30 minutes. Let cool, lift gingerbread out with the edges of the paper and cut into 12 squares.