@tashaleeministry Preheat oven to 350 degrees. Line a half-sheet (13 by 18-inch) pan with foil and grease with butter or cooking spray.
Beat the 1 cup butter and 3 cups brown sugar using an electric mixer with a paddle attachment until fluffy (approximately 2 minutes).
Add eggs one at a time while beating on medium-low speed and then add vanilla extract. Beat for 1 more minute and scrape down sides of bowl to make sure everything is even in consistency.
Combine the dry ingredients, flour, baking powder, and salt in a medium bowl.
Beat flour mixture into butter mixture at low-speed.
Stir in pecans and pour into prepared pan. Use a spatula to spread the batter evenly.
Bake for 25 to 30 minutes.
Bars should be set and slightly puffed. Cool completely.
For icing, melt 1 cup butter and 2 cups brown sugar in a saucepan over medium heat. Once mixture starts to bubble, decrease heat to medium-low and continue to cook for 2 more minutes, stirring occasionally.
Place powdered sugar, half-and-half, and vanilla extract in a mixing bowl and using a paddle attachment beat on medium speed until creamy.
Add melted butter mixture and beat to combine.
Pool over cooled bars and let icing set for 30 minutes before cutting