In a bowl, whisk together the flour, baking soda and salt. In a large bowl, combine the butter, chocolate, hot coffee and orange liqueur; stir occasionally until the chocolate and butter melt. Stir in the sugar until dissolved and the mixture is completely cool. Add the flour mixture in 2 batches, whisking between additions. Whisk in the eggs and vanilla. Divide the batter evenly between the 2 prepared pans and bake in the middle of the oven for 1 1/4 hours, or until a toothpick inserted in the center of the cakes comes out clean. Let the cakes cool completely on a rack. Refrigerate for at least 6 hours or overnight.