Preheat your oven to 180°C (350°F) and prepare an 8-inch square baking pan by greasing it and lining with parchment paper.

In a mixing bowl, cream the unsalted butter and packed brown sugar together using an electric mixer for about 2-3 minutes until fluffy.

Add the unsulphured molasses to the creamed mixture and mix thoroughly until glossy and combined.

Incorporate the egg and egg yolk into the mixture along with the vanilla extract and beat until the mixture is smooth.

In a separate bowl, whisk together the flour, baking soda, cinnamon, ginger, nutmeg, and salt, then fold into the wet mixture until just combined.

Fold in the white chocolate chips evenly throughout the batter.

Spread the batter into the prepared baking pan and bake for 20-25 minutes until a toothpick comes out with moist crumbs.

Cool in the pan for 1-2 hours before drizzling with melted white chocolate.

Cut into 16 squares and serve after the drizzle has set.