Pat chicken dry with paper towels; toss with 1 teaspoon salt, 1/2 teaspoon pepper, and cornstarch. Combine broth, lemon zest and juice, sugar, sesame oil, ginger, and 1 teaspoon salt; stir until sugar dissolves. In a large skillet (preferably cast-iron) over medium-high, heat 1/4 cup safflower oil until shimmering. Add beans and cook, stirring occasionally, until they blister in places, 3 minutes. Transfer to paper towels with a slotted spoon; sprinkle with salt.

Add 1/4 cup safflower oil to skillet; heat 1 minute. Add chicken; cook, stirring once, 4 minutes. Transfer to paper towels; discard oil. Add broth mixture. Simmer, scraping up browned bits with a spatula, 1 minute. Return chicken and beans to skillet. Simmer until sauce thickens and coats chicken, 2 to 3 minutes. Serve over rice.