Begin by preheating your oven to 400°F (200°C). As it warms, take each beet and wrap it individually in aluminum foil, creating a snug package. This will help to steam the beets as they roast, ensuring they cook through evenly and retain their moisture.
Place the foil-wrapped beets on a baking sheet and slide them into the oven. Roast for about 1 hour, or until they can be easily pierced with a fork. The sweet, earthy aromas will be a telltale sign they're nearing readiness.
While the beets are roasting, take a moment to prepare the walnuts. Heat a skillet over medium heat, add the chopped walnuts, and toast them, stirring frequently, until they're golden and fragrant, about 5 minutes. This will enhance their nutty flavor, adding depth to the salad.
Once the beets are done, carefully remove them from the oven and let them cool just enough to handle. By using a vegetable peeler or the edge of a spoon, gently peel away the skin, which should slide off easily thanks to the roasting process.
Proceed to cut the beets into bite-sized wedges or slices, whichever you prefer. Their rich, jewel-like color will add a beautiful contrast to the greens.
In a large mixing bowl, whisk together the balsamic vinegar, olive oil, Dijon mustard, and honey if you're using it. Season this dressing with salt and pepper to taste. The dressing should have a harmonious balance between the tangy vinegar and the smooth, rich oil, with a hint of piquancy from the mustard.
Add the mixed salad greens to the dressing and toss gently until each leaf is lightly coated. The greens will glisten with the dressing, ensuring every bite is flavorful.
To assemble the salad, lay a bed of the dressed greens on a serving dish or divide them among individual plates. Scatter the roasted beet pieces over the greens, followed by the toasted walnuts and crumbled goat cheese. The goat cheese will add a creamy, tangy element that pairs wonderfully with the sweet beets and earthy walnuts.
If desired, garnish with fresh herbs for an additional burst of color and freshness.
Serve immediately, offering an extra drizzle of olive oil or balsamic vinegar on the side for those who prefer a bit more dressing.