Place rack in the upper third of the oven; preheat broiler.
Place asparagus (or snow peas) in a medium microwave-safe bowl with 1 teaspoon water. Cover and microwave until tender, about 30 seconds. Add crab, celery, bell pepper, scallion, lemon juice, mayonnaise, Old Bay seasoning, hot sauce to taste and pepper; stir to combine.
Place English muffin halves, cut-side up, on a large baking sheet. Spread a generous 1/4 cup of the crab salad on each muffin half and sprinkle each with 1 tablespoon cheese. Broil until the cheese is melted, 3 to 6 minutes.