Preheat oven to 350°F (175°C). Line an 8x8-inch square baking pan with parchment paper.
Make the Shortbread Base: In a bowl, cream butter and sugar until fluffy. Add salt and flour, mixing until dough forms. Press evenly into pan. Bake for 20-22 minutes until lightly golden. Let cool.
Make the Caramel: In a heavy saucepan, combine butter, brown sugar, corn syrup, and sweetened condensed milk. Cook over medium heat, stirring constantly until mixture boils. Continue stirring 5-7 minutes until thickened and golden (soft ball stage, 235°F). Remove from heat and stir in salt and vanilla.
Pour caramel over cooled shortbread layer. Smooth evenly. Chill 30 minutes until set.
Make the Chocolate Topping: Melt chocolate and coconut oil together in microwave or over a double boiler until smooth. Pour over caramel and spread evenly.
Chill again for 20-30 minutes until chocolate is firm but not hard.
Slice into bars using a hot knife (wipe between cuts for clean slices).