Preheat oven to 180°C/160°C fan-forced. Line a large baking tray with baking paper.
Trim the top off the cob loaf. Leaving a 1cm edge, scoop bread from the centre of cob loaf. Cut bread and bread top into pieces. Place on the prepared tray. Arrange bread pieces around the cob on the tray.
Heat extra virgin olive oil in a large frying pan over medium heat. Add green onion. Cook, stirring, for 2 to 3 minutes or until softened. Remove from heat. Add cream cheese, sour cream, beer and 2 teaspoons VEGEMITE. Mix well until smooth. Stir in cheddar cheese. Season with salt and pepper. Spoon mixture into cob. Spray with olive oil spray.
Bake for 20 to 25 minutes or until golden.
Place butter and remaining Vegemite in a small microwave-safe bowl. Microwave on MEDIUM-HIGH (75%) for 30 to 40 seconds or until butter is melted. Using a fork, whisk mixture until just combined. Gently brush the top of dip with VEGEMITE mixture. Sprinkle with chives. Serve with corn, cucumber and crackers.