In a mixing bowl, sift together the flour, baking powder and salt. Stir in chopped thyme and set aside.
Using a stand mixer fitted with the paddle attachment, cream together the (room temp) butter, sugar, lemon zest and ground ginger until well combined. Stir in the egg and lemon juice. Slowly add in the dry ingredients and mix until the dough comes together.
On a clean, flat surface, divide the dough in half and shape into logs. Wrap with plastic wrap and refrigerate for at least 2 hours.
When ready to bake, preheat your oven to 340° F
Unwrap dough and slice the cookie log and place the cookie dough slices on a parchment paper-lined baking sheet. Lightly brush the cookies with milk and bake for about 12-15 minutes, or just until the edges turn golden.
While the cookies are cooling, microwave the chopped chocolate in 30-second increments, stirring after each 30-second increment, until melted. Dip half of each COOLED cookie into the chocolate; and transfer back to the parchment-lined baking sheet. Chill until set, for about 10 minutes.