Toast the walnut halves in a dry skillet over medium heat, stirring often, until fragrant and lightly darkened, 5β7 minutes. Transfer to a plate to cool.
In a large mixing bowl, whisk the minced shallot, white wine vinegar, Dijon mustard, honey, kosher salt, and black pepper. Slowly drizzle in the extra-virgin olive oil while whisking until the dressing is emulsified.
Quarter, core, and thinly slice the pears, then toss them with the lemon juice to prevent browning.
Add the baby arugula, pears, and cooled walnuts to the bowl with the dressing. Toss gently until everything is lightly and evenly coated.
Scatter the crumbled blue cheese over the salad and toss once more very gently, or leave the cheese on top. Taste and adjust seasoning if needed. Serve immediately.