Line a 13x9-inch baking pan with foil, ensuring the foil extends over the edges, and grease the foil.
In a medium saucepan, cook and stir the brown sugar, 2/3 cup butter, and 1/2 cup maple syrup over medium heat until the butter is melted.
Let it cool slightly.
Add the eggs and vanilla, stirring until well combined.
Stir in the flour, baking powder, and baking soda.
Gently fold in the frozen raspberries.
Spread the batter evenly in the prepared pan.
Bake for 25 to 30 minutes or until a toothpick inserted comes out clean.
Allow the bars to cool in the pan on a wire rack.
For the frosting, in a medium bowl, stir together the powdered sugar, 1/4 cup maple syrup, 2 tablespoons softened butter, and 2 tablespoons milk until the mixture is smooth.
Spread the frosting over the uncut bars.
Spoon raspberry preserves in small mounds onto the frosting.
Use a narrow metal spatula to gently swirl the raspberry preserves to create a marbled effect.
Use the foil to lift out the uncut bars, then cut them into individual bars.
Notes / Tips / Wine Advice:
Yields: 36 servings (1 bar each)Storage: Place the bars in a single layer in an airtight container. Store them in the refrigerator for up to 3 days or freeze them for up to 3 months. Enjoy your Maple Raspberry Delight Bars!