Preheat oven to 200C. Line a large baking tray with baking paper.
In a large bowl mix together the cream cheese, mayonnaise, sour cream, horseradish, mustard powder and Worcestershire until well combined.
Fold through the Swiss cheese, spring onion and crumbled Huon Salmon. Season to taste and set aside, or cover and refrigerate if making ahead.
Cut 4cm off top of the loaf to form a lid. Scoop bread from centre of loaf, leaving 1.5cm edge. Cut slices around the outside of the bread round, at about 2cm intervals, slicing about 2/3 of the way down the side. Tear or roughly chop bread pieces and the lid.
Spoon mixture into loaf and place on prepared tray. Sprinkle over parmesan cheese. Arrange bread pieces in a single layer around loaf and drizzle the loaf and the pieces with olive oil.
Bake for 20 minutes or until dip is warm and cheese golden.