Preheat oven to 350 degrees F. Grease a 13x9x2-inch baking pan; set aside. Place molasses in a 2-cup glass measure; add enough water to measure 1-1/3 cups total liquid and stir to combine. Transfer to a large mixing bowl. Add 1 tablespoon coffee crystals; stir to dissolve. Add dry cake mix, eggs, and oil. Beat with an electric mixer on low speed until combined. Beat on medium speed for 2 minutes. Spread batter evenly in prepared pan or dish. Bake about 30 minutes or until a toothpick inserted in center comes out clean. Cool in pan on a wire rack.
While cake is cooling, in a small bowl, stir together flour, brown sugar, and cinnamon. Using a pastry blender, cut in the 3 tablespoons butter until crumbly. Stir in pecans. Knead with fingers until mixture starts to cling together (mixture should form small moist clumps). Spread clumps evenly in a 10x15-inch baking pan. Bake in the 350 degree F oven about 10 minutes or until lightly golden brown. Transfer to a piece of foil to cool.
For frosting, in a large mixing bowl, beat the 1/4 cup butter with an electric mixer on medium speed for 30 seconds. Add 1 cup of the powdered sugar; beat until combined. In a small bowl, stir together the 1/4 cup half-and-half and the 1 teaspoon instant coffee crystals until dissolved. Add to powdered sugar mixture along with vanilla. Beat until combined. (Mixture may appear curdled.) Gradually add the remaining 2-1/2 cups powdered sugar, beating until smooth. If necessary, beat in enough additional half-and-half to make frosting of spreading consistency. Spread frosting over cooled cake; sprinkle with toasted pecan mixture. Makes 16 servings.