Add the molasses and egg. Mix until well combined, scraping down the sides of the bowl as needed.

In a separate bowl, whisk together the flour, ginger, cinnamon, cloves, baking soda, and salt.

Gradually add the dry ingredients to the wet ingredients, mixing until a soft dough forms.

Cover and refrigerate the dough for 1 hour.

Preheat the oven to 350°F and line baking sheets with parchment paper. Scoop the chilled dough into 1-tablespoon portions, roll into balls, and lightly roll each ball in granulated sugar.

Place the dough balls about 2 inches apart on the prepared baking sheets. Gently press an indentation into the center of each dough ball, about one-third of the way down, using your thumb or the back of a small measuring spoon. Avoid pressing too deeply, which can cause the dough to crack.

Bake for 9–10 minutes, until the edges are set.

Immediately after removing the cookies from the oven, gently press the centers again to restore the indentations.

Let the cookies rest on the baking sheet for a few minutes, then transfer them to a wire rack to cool completely.

Heat the heavy whipping cream in a small saucepan or microwave until steaming hot but not boiling.

Place the white chocolate chips in a heat-safe bowl. Pour the warm cream over the chocolate chips, making sure they are mostly covered. Let stand for 5 minutes to allow the chocolate to melt.

Stir the chocolate and cream together until the ganache is smooth and creamy. If some chocolate pieces remain unmelted, let the mixture stand briefly longer before stirring again.

Allow the ganache to stand for another 5 minutes so it thickens slightly before spooning it into the cookies. It may look thin or slightly translucent while warm; it will become thicker and more opaque as it cools.

Spoon the ganache into the center of each completely cooled cookie. Add Christmas sprinkles while the filling is still soft, if desired.

Allow the filling to cool and firm up before serving or storing the cookies.