Heat 3-4 quarts water to just below boiling point. Add vinegar and pinch of salt. Gently stir the water. Lower heat so water is simmering. Crack eggs into the water one at a time and poach gently for 4-5 minutes. Remove with slotted spoon and season with salt and pepper.
Meanwhile, heat griddle or skillet over medium heat; fry Canadian bacon until lightly browned. Remove from griddle; set bacon aside. Add 1 tablespoon butter to skillet. Spread each bottom half of English muffins with 1 tablespoon Sharp Cheddar cheese spread. Place in heated skillet. Top each bottom in pan with 1 slice Gouda, about 1 ounce spinach, 2 slices Canadian bacon, and 1 slice tomato. Cook over medium heat until cheese is melted. Remove to a plate and top each with a poached egg. Serve open-faced with remaining muffin halves, toasted and buttered, on the side.