Preheat the oven to 375
Cut challah bread into 1 inch thick cubes. Set aside.
In a large bowl, combine eggs, Ontario milk, Ontario cream, thyme, pepper and salt until smooth
In a large baking dish, brush all sides evenly with melted Ontario butter. Add a layer of challah bread cubes and evenly distribute a third of the caramelized onion and Ontario Aged White Cheddar cheese. Repeat until the dish is full. Pour egg mixture over bread, cover with plastic wrap and let sit for 5 minutes, until the mixture absorbs.
Bake for 30 minutes or until golden brown. Serve.