How do you define it? Is it based on ingredients? Techniques? Percentage of dishes using "non-traditional" ingredients or techniques?
1. Hong Kong-style cafes have both Western and Chinese dishes (e.g spaghetti, chow fun).
2. A Cantonese restaurant serves Shandong dishes (e.g. scallion pancakes)
3. An American restaurant uses Sichaun peppercorn for one of their otherwise traditional beef dishes.
4. Any European, Asian, or African restaurant using tomatoes or potatoes.
Do they qualify as fusion restaurants?
At what point does such an ingredient stop being considered exotic and becomes an integral part of the cuisine?