To make it...
Bring a large saucepan of lightly salted water to a boil. Drop in the green beans and cook, uncovered, 5 to 7 minutes or until tender but still crisp. Drain. (Can be made ahead to this point. Rinse with cold water to stop the cooking. Place in a resealable plastic bag and refrigerate.) Dry the saucepan and return it to the stove. Toast the mustard seeds over low heat just until they pop, about 1 minute, stirring to prevent scorching. Add the honey and vinegar and cook until the sauce boils and becomes syrupy. Add the green beans and toss.
To fake it...and save 15 minutes
Thaw three 9-ounce packages whole green beans under warm running water. Place in a skillet with 1/2 cup bottled honey-mustard salad dressing. Over medium heat, toss until heated through, adding more dressing if necessary to lightly coat all the green beans.