Bring a medium pot of water to a boil. Add snap peas to the boiling water and cook for just 1 1/2 minutes to blanch. Drain snaps peas quickly in a colander.

Heat a saute pan or wok over medium-high heat and add oil. Add mushrooms, leek, ginger, and garlic to the hot oil; saute for 1 minute. Add snap peas and bell pepper; cook, stirring regularly, for 1 to 2 minutes. Add red pepper flakes, sugar, and soy sauce. Stir thoroughly. Season with salt and pepper.