Process the raisins and ginger in a food processor until the mixture sticks together, about 10 seconds. Transfer the mixture to a large bowl. Heat butter in a small saucepan over medium-low heat, swirling the pan occasionally, until nutty brown in color, about 10 minutes. Stir in cinnamon and allspice, cook an additional 15 seconds, then remove from heat. Stir butter mixture into raisin mixture until well combined; allow to cool completely.

In a small bowl, whisk together the flour, baking soda and salt. Whisk brown sugar, molasses, and eggs into raisin mixture until combined. Using a rubber spatula, fold in flour mixture (the dough will be very sticky). Cover bowl with plastic wrap and refrigerate at least 1½ hours, or up to 24 hours.

When ready to bake, adjust oven racks to upper-middle and lower-middle positions and preheat oven to 350F. Line two baking sheets with parchment paper. Divide dough into quarters. Working with one piece of dough at a time, transfer to a lightly floured surface and roll into a 10-inch log. Transfer to a parchment-lined baking sheet and square off the sides. Repeat with remaining pieces of dough, placing two logs on each baking sheet.

Bake until only a shallow indentation remains on the edges when touched, 15-20 minutes, rotating sheets halfway through baking. Cool on baking sheets 5 minutes, then transfer to wire racks to cool completely.

In a small bowl, whisk together orange juice and powdered sugar until smooth. Drizzle glaze onto cooled log and let sit until the glaze hardens, about 15 minutes. Cut logs into 2-inch bars. Cookies can be stored in an airtight container at room temperature for up to 5 days.