Preheat the oven to 350°F. Liberally spray a 13x9-inch metal baking pan with cooking spray. Set aside.
Spread pecans in a single layer on a sheet pan. Toast in a preheated 350°F oven for 6-8 minutes or just until lightly golden and fragrant. Set aside to cool.
In a medium size heavy bottomed saucepan melt the butter over medium heat. Add the brown sugar. Simmer while stirring constantly until the sugar has dissolved. Remove from the heat and cool to warm.
Once cooled, use a hand mixer to beat the eggs into the warm sugar mixture one at a time beating well after each addition, then add the vanilla extract.
In a large bowl use a whisk to sift together the flour, baking powder and salt.
Gradually beat the dry ingredients into the creamed butter-brown sugar mixture.
Assemble the Turtle Bars: Pour 1/2 of the batter into the pan. Top with 1/2 of the Rolo candies and 1/2 of the toasted pecan pieces.
Pour the remaining batter on top. Roughly chop the remaining Rolo candies and sprinkle over the batter. Top with a sprinkle of pecans. (Reserve 2 Tbsp for garnishing.)
Bake for 38-40 minutes or until the top is golden brown and a toothpick inserted into the center shows moist crumbs. (Tip: Test the batter only to check for doneness, the melted caramel will be gooey.)
Cool the turtle bars in the pan on a wire cooling rack.
Chocolate Drizzle: In a microwave safe bowl, melt together the chocolate chips and vegetable shortening. Heat in 20 second increments stopping to stir each time. Repeat the process until completely smooth.
Drizzle over the cookie bars and garnish with reserved pecans. Slice and serve.