Preheat oven to 350F; butter and flour a 9x13 inch pan.
Sift together the flour, cocoa, baking soda and salt; set aside.
In a large bowl, cream together the butter and sugar until light and fluffy; beat in the eggs one at a time, then stir in the vanilla and coffee liquid (if using); beat in the flour mixture alternately with the milk, mixing just until incorporated; pour HALF of batter into prepared pan; bake in the preheated oven for 15 minutes.
Meanwhile, in heavy saucepan over low heat, melt caramels and butter; remove from heat; add condensed milk and mix well; spread caramel mixture evenly over cake; spread remaining cake batter over caramel mixture; top with nuts; return to oven; bake 30 to 35 minutes longer or until cake springs back when lightly touched.
A dollop of freshly-whipped cream on each piece is not a bad thing!