Line a sheet pan with a silpat mat. Alternatively, you can spray with cooking spray. In a small bowl, combine the baking soda, ginger, cinnamon, and nutmeg.
¼ teaspoon baking soda, ¼ teaspoon ground ginger, ⅛ teaspoon ground cinnamon, ⅛ teaspoon ground nutmeg
In a heavy bottom saucepan, add light brown sugar, unsalted butter, molasses, and water. Stir to combine over medium-high heat. Bring to a boil and reduce heat to medium-low. Cover with lid for 1 minute to wash any sugar residue off the sides of the pan.
1¼ cup light brown sugar, ½ cup unsalted butter, 2 tablespoons molasses, 2 tablespoons water
Uncover and clip on candy thermometer. Cook the candy mixture without stirring until the temperature reaches 285°F. Remove from heat immediately. Note: Depending on your stove you may have a 'hot spot' on your burner. To keep the sugar from burning, you can "move" the mixture around gently with a rubber spatula occasionally but this may extend the cooking time slightly. Add vanilla extract and baking soda and spice mixture. Stir vigorously for about 10 turns of a nonstick spatula and immediately pour over the prepared baking sheet. Spread the toffee evenly over the surface until about ¼-inch in thickness. Work quickly to spread the toffee, it will set within 30 seconds.
1 teaspoon pure vanilla extract
While the toffee is still warm, sprinkle evenly with the white chocolate chips and allow the heat from the toffee to melt the chips, this will take about 60 to 90 seconds. Spread the melted chocolate evenly over the toffee. Top with crushed gingerbread or slivered almond pieces while the chocolate is still warm.
1 cup white chocolate chips, ¾ cup crushed gingerbread cookies or slivered almonds
Place the pan in the refrigerator until the toffee is firm, about 15-20 minutes. Turn out onto a cutting board, using a sharp knife cut into slightly larger than 'bite-sized' pieces, or break it apart with your hands. Store in an airtight container at room temperature.