1Heat oven to 350°F (if using dark or nonstick pan, heat oven to 325°F). Grease 13x9-inch pan with shortening or spray with cooking spray.
2In large bowl, beat brown sugar, butter and egg with electric mixer on medium speed, or mix with spoon. Stir in flour and oats. Spread in pan. Bake 15 to 20 minutes or until light golden brown.
3Meanwhile, in 1-quart saucepan, heat caramels and half-and-half over low heat, stirring occasionally, until caramels are melted. Pour caramel mixture over crust. Sprinkle with chocolate chunks, nuts and pretzels.
4Bake 5 to 8 minutes or until chocolate is softened. Cool about 1 hour or until chocolate is set. For bars, cut into 6 rows by 6 rows.