Bring a medium sauce pot of generously salted water to a boil. Add the fusilli and cook until tender, 12 to 15 minutes. Drain and set aside.
While the water heats and the fusilli cooks, prepare the vegetables.

• Peel and thinly slice the red onion.
• Thinly slice the mushrooms.
• Finely chop, press, or grate enough garlic to measure 1 teaspoon.
• Rinse the cannellini beans.
• Snap off the woody ends from the asparagus; cut the asparagus into 2-inch pieces.
• If using, remove the stem, ribs, and seeds from the poblano; thinly slice the poblano. Wash your hands after handling.

In a large frying pan over medium-high heat, warm 1 tablespoon oil until hot but not smoking. Add the onion, mushrooms, and garlic, season with salt and pepper, and cook, stirring occasionally, until the onion and mushrooms start to soften, 3 to 5 minutes. Stir in the beans, asparagus, and as much poblano as you like, and cook until the asparagus and poblano are crisp-tender, 1 to 2 minutes.
While the vegetables cook, prepare the basil-yogurt dressing.

• Zest and juice the lemon, keeping the zest and juice separate.
• Strip the basil leaves from the stems; coarsely chop the leaves. Set aside half for garnish.

In a small bowl, stir together the yogurt, lemon zest, 1 tablespoon lemon juice, and half the basil. Season to taste with salt and pepper.

In a large bowl, combine the fusilli and vegetables. Fold in the arugula and feta. Drizzle with as much basil-yogurt dressing as you like and toss to coat. Season to taste with salt and pepper.

Transfer the fusilli salad to individual bowls and garnish with the remaining basil. Serve the remaining dressing on the side.