Step 1

Preheat the oven to 350 degrees F. Line a rimmed baking sheet with parchment.

Step 2

Pulse the flour, granulated sugar, gingerbread spice, baking powder and salt in a food processor until combined. Add the butter and pulse until the butter is thoroughly combined with the dry ingredients and the mixture looks sandy. Transfer to a large bowl.

Step 3

Whisk together the molasses, vanilla, eggs and 1 tablespoon water in a small bowl; stir into the flour mixture until a crumbly dough forms. Press together and knead into a moist, uniform dough.

Step 4

Divide the dough in half and place on the prepared baking sheet. Shape the dough into two 10-by-2-inch logs, keeping 3 inches between the logs. If the dough is sticky, splash a couple drops of water on your hands and continue shaping. Bake until the outside is set but the inside is still slightly soft, about 30 minutes.

Step 5

Let cool for 5 minutes on the baking sheet. Transfer the logs to a cutting board and slice 1/2 inch thick on the bias with a serrated knife. Return the slices to the baking sheet, slat-side down, and bake, flipping the slices halfway through, until crisp, 20 to 25 minutes. Transfer the biscotti to a wire rack to cool.

Step 6

Once the biscotti are cool, combine the white chocolate and oil in a medium microwave-safe bowl. Microwave on high in 30-second increments, stirring occasionally, until melted and smooth, about 1 1/2 minutes total. Dip half of each biscotti at an angle in the white chocolate, letting the excess drip off. Return to the wire rack, then refrigerate until just set, about 5 minutes.

Step 7

Pour the remaining white chocolate mixture into a small piping bag or resealable bag, then snip the tip or corner with kitchen shears to create a small hole. Drizzle the white chocolate at an angle across the dipped end of each biscotti, drizzling in the opposite direction to create a crisscross pattern. Return to the wire rack, then sprinkle with sanding sugar. Refrigerate until all the chocolate is completely set, about 10 minutes. The biscotti can be stored in an airtight container for up to 1 week.