Place the cheese and cornstarch in a small saucepan and toss to combine. Add 1 cup of the evaporated milk and cook over low heat, whisking constantly until the cheese has melted and the dip thickened, 10 to 15 minutes. Add evaporated milk as necessary to thin out the dip.
Fold in the salsa, and the hot-pepper sauce (if using). Remove the pan from the heat and serve the dip immediately with the bread cubes.
Tip: If the dip looks grainy instead of smooth, puree it with a stick blender before folding in the salsa. To keep the dip warm, serve it in a preheated stoneware bowl set over a cloth-covered heating pad.