In a large bowl, whisk together the flour, ground ginger, cinnamon, baking soda, nutmeg, and salt. Set aside.
In a separate bowl using an electric mixer, beat the softened butter and brown sugar on medium speed until light and fluffy, about 2-3 minutes. Add the molasses, egg, and 1 teaspoon of vanilla extract and mix until just combined.
Gradually add the dry ingredients to the wet ingredients, mixing on low speed until a soft dough forms. Do not overmix.
Shape the dough into a flat disk, wrap it tightly in plastic wrap, and refrigerate for at least 4 hours or overnight.
When ready to bake, preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper.
Shape the chilled dough into 1-inch balls. Roll each ball in the granulated sugar to coat completely and place them 2 inches apart on the prepared baking sheets.
Bake for 8 to 10 minutes, or until the edges are set and just beginning to brown. The centers will still be soft.
Immediately press one unwrapped chocolate candy into the center of each warm cookie. The cookie will crack slightly around the edges. Let the cookies cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.
For the drizzle, whisk together the confectioners' sugar, milk, and 1/4 teaspoon of vanilla in a small bowl. Stir in the corn syrup until the mixture is smooth. Drizzle over the cooled cookies.