Begin by rinsing the green beans under cold water. Trim the ends of the beans to remove any tough or fibrous parts. Set them aside while you bring a large pot of salted water to a boil.
Once the water is boiling, add the green beans and cook for about 3-4 minutes, or until they are bright green and tender-crisp. Drain the beans in a colander and immediately plunge them into a bowl of ice water to stop the cooking process.
While the green beans cool, prepare the balsamic date reduction. In a blender or food processor, combine the warm water and pitted dates. Blend until smooth. Then, add the balsamic vinegar and blend again until fully incorporated.
In a large skillet, heat the olive oil over medium heat. Add the blanched green beans and sauté for about 2-3 minutes, just until heated through. Season with salt and pepper to taste.
Remove the skillet from heat and drizzle the balsamic date reduction over the sautéed green beans. Toss gently to coat the beans evenly. Transfer the beans to a serving dish and sprinkle with crumbled feta and toasted pine nuts.