Shallots (Best Option)
1 tablespoon finely minced shallots per 1 medium onionShallots are closely related to onions but have a milder, sweeter flavor profile that integrates well into delicate dishes like Crème Brûlée. Their fine texture when minced ensures they dissolve or blend into the custard base, maintaining smoothness.
For best results, mince shallots very finely and gently cook or macerate them to soften their sharpness before incorporating. Avoid using raw shallots to prevent any harsh bite.
Using shallots preserves the intended subtle onion flavor without compromising the creamy, smooth texture of the dessert, making them the closest match to onion in this context.