Prepare mushrooms, carrots, broccoli and lemon as noted above.
Saute mushrooms in 2 Tbsp butter until soft. Stir in carrots and saute until tender-crisp. Add broccoli and saute until tender-crisp. (Don't overcook broccoli! should remain bright green.) Stir in lemon slices.
Combine sugar with melted butter. Add to vegetables. Stir until everything is well-glazed.