Pre heat oven to 350 degrees F.
Line a 13X9 pan with parchment paper
In a medium bowl whisk together flour, ginger, allspice, salt, baking soda and crystallized ginger.
In another bowl stir together molasses, eggs, brown sugar and butter.
combine wet and dry ingredients, beat until smooth.
Spread batter in prepared pan.
Blend together with pastry blender or fingers, butter, flour, salt, and brown sugar until fairly well blended. Ok if some lumps of butter remain. Stir in crystallized ginger.
Bake base for 15 minutes. Top with streusel and bake an additional 30 minutes or until deep golden brown.
Remove squares from oven, run a knife around edges to loosen. Cool.
Cut into squares.