Preheat the oven to 350°F (175°C).

In a mixing bowl, cream together the softened butter and granulated sugar until light and fluffy.

Add the eggs one at a time, mixing well after each addition.

Stir in the vanilla extract and watermelon puree until combined.

In a separate bowl, whisk together the flour and baking powder.

Gradually add the dry ingredients to the wet mixture, mixing until just combined.

Fold in the chocolate chips.

Roll the dough out on a floured surface and use a cookie cutter to cut out watermelon slice shapes.

Place the cookies on a baking sheet and bake for 12-15 minutes or until lightly golden.

Allow cookies to cool completely on a wire rack.

In a bowl, mix the powdered sugar and milk until smooth.

Add green food coloring if desired to achieve a green hue.

Spread the frosting on top of the cooled cookies.