Preheat your oven to 350°F (175°C).
Line a baking sheet with parchment paper.
Melt the finely chopped semi-sweet chocolate with the melted butter using a double boiler or microwave until smooth and glossy. Let cool slightly.
Whisk together the all-purpose flour, baking powder, and salt in a separate bowl.
In a large mixing bowl, combine canola oil, 2 cups granulated sugar, light corn syrup, eggs, egg yolk, vanilla extract, and creme de menthe flavoring. Beat with a whisk until well combined.
Add the melted chocolate mixture to the wet ingredients and stir until fully incorporated.
Gradually fold in the dry ingredients with a rubber spatula until no flour streaks remain and dough is thick and slightly sticky.
Cover the dough and refrigerate for at least 30 minutes.
Scoop tablespoon-sized portions of dough, roll into balls, then roll each ball in granulated sugar followed by confectioners sugar.
Place the sugar-coated dough balls on the prepared baking sheet about 2 inches apart and bake for 10-12 minutes until crinkled on top and edges are set.
Allow cookies to cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.