Place the sugar in a large, heavy pot and set it over a medium heat. Stirring often, slowly let the sugar melt and caramelize until dark brown, being careful not to let it burn. Add 2 cups of dark corn syrup. Add 1 cup of water along with the coffee and butter. Bring the pot to a boil, lower to a simmer and cook, stirring occasionally, for about 30 minutes. Remove the pot from the heat and allow it to cool to room temperature. If the sauce is too thick, add a little water.
Add the roasted pecans shortly before serving so they will maintain their crispness. Without the pecans added, the sauce will keep for several weeks in a covered container. If you choose to refrigerate it, which is unnecessary, be sure to let it get back to room temperature before serving.