When ready to cook, start the Traeger grill on Smoke with the lid open until the fire is established (4 to 5 minutes). Set the temperature to 400 degrees F and preheat, lid closed, for 10 to 15 minutes.
Lay the asparagus in a single layer on a rimmed baking sheet. Drizzle with 2 tablespoons of the oil (use more if needed) and season the asparagus with salt and pepper.
Arrange the asparagus spears directly on the grill grate (perpendicular to the bars so they doesn't fall through) and grill until the spears are tender and charred in spots, 10 to 15 minutes, depending on their thickness. Remove from the grill and slice the asparagus spears on a diagonal into 1-inch pieces and set aside; leave the grill on.
On the stovetop, warm a Dutch oven over medium heat. Add 3 tablespoons of olive oil to the pan. Add the shallots and cook, stirring often, until they are soft and translucent. Add the garlic and cook for an additional minute. Add the rice and stir to coat the grains with the olive oil. (A metal spatula or pancake turning works well for this as its flat edge efficiently moves the rice around.)
Pour the white wine into the pan, stirring, until the liquid has been absorbed by the rice. Stir in the thyme, lemon zest, and 3-1/2 cups of broth into the rice mixture.
Increase the heat to medium-high; bring the liquid to a simmer. Keep the remaining broth hot. Put the lid on the pot and transfer to the grill grate.
Bake the risotto, stirring once halfway through the cooking time, for 25 to 30 minutes, or until most of the liquid has been absorbed. (Add 1/2 cup additional broth to the pot if the rice seems dry). When cooked, the rice should be just tender, but not mushy. "Al dente," the Italians call it.
Stir in an additional 1 cup of broth (or more if you like your risotto creamier), the Parmesan, and the butter, 2 pieces at a time, stirring vigorously.
Finally, gently fold in the chives, if using, and the reserved asparagus. Taste for seasoning, adding salt and pepper as desired. Transfer to a bowl or bowls and serve immediately.