Step 1

In a small bowl, whisk the soy sauce, water, dry sherry, sesame oil, sugar, cornstarch, red pepper flakes and mustard together. Set aside.

Step 2

Heat 2 tablespoons oil in a 12-inch nonstick skillet over high heat until very hot and shimmering. Add the beans and cook, stirring frequently, until tender, puckered and browned, about 7-10 minutes (cooking time will depend on the size of the beans). Transfer beans to large plate.

Step 3

Add 1 teaspoon oil to pan. Add shiitake mushrooms and cook, stirring occasionally, for 3-4 minutes until slightly browned. Reduce heat to medium, then add the garlic and ginger and cook, stirring constantly, until fragrant, about 20 seconds. Return the beans to the pan and add the sauce. Toss and cook until the sauce is slightly thickened and the vegetables are evenly coated, about 10 seconds. Transfer to serving dish and serve immediately.

Step 4

Note: This recipe works best with thinner green beans (but not the super thin French haricots verts). If your beans seem really long, thick or a bit tough, cut them in half so they cook evenly (there may be just a few in the bunch that you need to cut). Also, be sure beans are dry, otherwise oil will splatter.