Cover a 9 x 9 inch OR 8 x 8 inch casserole dish with foil over flowing from dish. Spray with cooking spray or butter; set aside.
Caramel Layer - In a small saucepan over medium heat, melt caramel candies, milk and butter. Stir occasionally and turn heat down if needed to avoid burning candy. Melt and stir caramel mixture until silky smooth. Remove from heat. Set aside 1/2 cup caramel sauce for topping.
Bottom Layer - In a medium saucepan over low heat, melt 14 oz. sweetened condensed milk and 12 oz. semi-sweet chocolate chips. Stir occasionally and turn heat down if needed. Stir in butter and vanilla extract. Whip mixture until glossy and smooth. Remove from heat.
Pour chocolate into prepared dish. Evenly spread with spatula.
Pour caramel sauce over chocolate fudge in casserole dish. Evenly spread with spatula. Sprinkle with sea salt, if desired.
While the caramel cools down, make the top chocolate layer.
Top Layer - In a medium saucepan over low heat, melt 7 oz. sweetened condensed milk and 6 oz. (1 cup) semi-sweet chocolate chips. Stir occasionally and turn heat down if needed. Stir in butter and vanilla extract. Whip mixture until glossy and smooth. Remove from heat.
Pour chocolate over caramel layer and evenly spread with spatula.
Nut Topping - Top with whole pecans and pecan pieces. Drizzle remaining 1/2 cup caramel sauce over pecans. Sprinkle with sea salt.
Refrigerate for 3 hours.
Remove foil from dish by picking up the ends. Slice into 24-48 pieces of fudge. Fudge needs to stay refrigerated.