Mom's Favorite Chocolate Caramel Nut Squares

Line the inside of a 8 inch square baking pan with a square of buttered foil. Combine semisweet and milk chocolate chips and shortening in a small saucepan over low heat. Cook, stirring, until chocolate is melted and smooth. Spoon half of the melted chocolate mixture into the bottom of the prepared pan. Tilt pan to coat bottom. Refrigerate until chocolate is firm. Combine caramels, butter and milk in a medium saucepan over medium heat. Cook, stirring, until caramels are melted and smooth. Stir in pecans. Remove the pan from the heat and let the mixture stand until lukewarm. Spread the cooled caramel mixture into the prepared pan. Melt the remaining chocolate mixture in the microwave if necessary and spread over the caramel. Refrigerate until almost firm. Cut into squares. Store squares refrigerated.