Roast the goat cheese wedges. Place a rack in the middle of your oven and heat it to 400°F (200°C). Line a small baking sheet with parchment paper. Arrange the cheese wedges on the sheet, leaving space between each one. Bake for about 8 minutes — you want the edges just starting to soften but still holding their shape when you remove them.
Make the dressing. While the cheese bakes, whisk together the olive oil, Dijon mustard, honey, and apple cider vinegar in a small bowl until emulsified. Taste and add salt and pepper to your preference. The dressing should taste slightly stronger than you want it on the salad since the greens will dilute it.
Prepare the apples. As soon as the cheese is out of the oven (set aside to rest), slice the Granny Smith apples into thin half-moons about 1/8-inch thick. Toss them gently with a tablespoon of your dressing and set aside in a small bowl. Dressing the apples separately keeps their crunch intact until serving time.
Toast your nuts. While everything else is happening, toast the walnuts or pecans in a dry skillet over medium heat for 3-5 minutes, shaking the pan occasionally, until fragrant and lightly browned. Let cool slightly before roughly chopping.
Assemble the salad. On each serving plate (or one large platter), spread about half of your mixed greens. Top with the dressed apple slices, then place a warm goat cheese wedge on top of each portion. Sprinkle with toasted nuts and drizzle any remaining dressing over everything. Serve immediately while the cheese is still slightly warm.
