Preheat oven to 350º F (180 º C). Line a 13x9 baking pan with foil and lightly spray with cooking spray. Set aside.
In a small bowl, combine brown sugar, chopped dates, orange juice, orange zest, and lemon juice; mix to combine. Set aside.
In a large mixing bowl, stir together flours (AP and whole wheat), apple pie spice, baking soda, baking powder, and salt.
Add butter, yogurt, and maple syrup to the flour mixture and beat with an electric mixer on low until combined, scraping down the sides as needed. The mixture will be crumbly. Add dates mixture and mix until well combined.
Place dough in the prepared baking pan. With damp hands, spread the dough evenly.
Bake for 15 minutes, or until a wooden toothpick inserted in the center comes out clean.
Let it cool in the pan. Cut into bars. Drizzle with melted dark chocolate and sprinkle with sea salt, if desired.