Chop the oats, either in the bowl of a food processor, or by hand. Add the flour, baking powder, baking soda and salt to the oats, and mix together.
Mix the WowButter and softened butter, using either a hand mixer or a standing mixer, until combined. Add the 1/2 cup sugar and light brown sugar and beat about 3 minutes. Add the vanilla and egg and mix until well combined. Scrape down the sides of the bowl. Add the flour mixture in 2 batches, scraping the bowl each time.
Chill the dough until firm, about 1 hour. Preheat the oven to 350 degrees. Put the remaining 3 tablespoons sugar in a small bowl. Scoop a tablespoon-sized portion of the dough and roll into a ball with your hands. Roll each ball in the sugar to coat. Place the balls about 3 inches apart on parchment-lined baking pans. Bake 10 minutes.
Remove the pans from the oven and with the back of a 1/2 teaspoon measuring spoon, quickly make a "thumbprint" well in each cookie. Return the cookies to the oven for 5 minutes. Remove cookies from the pan and let cool on a rack.
Place the chopped chocolate in mixing bowl. Heat the cream to the boiling point and then pour over the chocolate. Stir gently until the chocolate is smooth and melted. Drop a small amount of chocolate in the "thumbprint" of the cooled cookie. Let the chocolate cool completely and then serve.