To prepare dressing: Heat a small dry skillet over medium-low heat. Add poppy seeds and toast, stirring, until fragrant, about 1 minute. Transfer to a small bowl (or jar) and let cool. Add oil, vinegar, mustard, honey, shallot, salt and pepper; whisk (or shake) until blended.
To prepare beans: Cook beans in a large pot of boiling water until just tender, 5 to 7 minutes. Drain. Warm the dressing in a large skillet over medium heat. Add beans and toss to coat.