Place a large rimmed baking sheet in oven; preheat to 450°F. Combine 1 teaspoon each garlic powder, oregano and paprika, ½ teaspoon black pepper and ¼ teaspoon salt in a small bowl; rub all over chicken. Drizzle 2 tablespoons oil onto the hot baking sheet. Using tongs, rub the chicken in the hot oil; arrange, rounded-side down, in a single layer. Roast until beginning to brown, about 5 minutes.

Meanwhile, cut lemon in half; thinly slice 1 half and juice the other half.

Combine mushrooms, the lemon slices and 1 tablespoon oil in a large bowl; toss to coat. Flip chicken over; carefully arrange the mushroom mixture around the chicken. Roast until an instant-read thermometer inserted into the thickest portion of chicken registers 170°F, about 20 minutes.

Meanwhile, place beans, ½ cup broth, 1 tablespoon oil, ½ teaspoon salt, the remaining 1 teaspoon garlic powder and the lemon juice in a food processor; process until smooth, about 1 minute. Transfer to a medium saucepan; cook over medium heat until warm, 5 to 8 minutes. Keep warm.

Add ½ cup each kale and cilantro, 2 tablespoons vinegar and ½ teaspoon garlic to a mini food processor; pulse until finely chopped, about 10 pulses. With the processor running, slowly pour the remaining 4 tablespoons oil through the chute; pulse until blended and spoonable, about 5 pulses. Transfer to a bowl; stir in the remaining ¼ teaspoon salt.

Spread the bean puree on a platter. Top with the chicken and mushroom mixture; drizzle with kale chimichurri. Garnish with chile rings, if desired.