These stuffed portobello mushrooms are a savory, crowd-pleasing appetizer. Tender mushroom caps are filled with a creamy blend of sautéed onion, cream cheese, and cheddar, then finished with a buttery Ritz cracker topping for irresistible crunch. Rich, cheesy, and perfectly bite-sized, they’re an elegant yet comforting dish that works beautifully for parties, holidays, or a cozy dinner spread.