Heat 1 tablespoon butter and olive oil in a large, heavy-bottomed saucepan over medium-high heat. Cook and stir onion in hot butter-oil until onion begins to turn golden brown at the edges, about 2 minutes. Pour in rice; stir until rice is coated in oil and has started to toast.

Reduce heat to medium and stir in white wine. Cook until mostly evaporated, then stir in 1/3 of the boiling vegetable broth; continue stirring until incorporated. Repeat this process twice more, stirring constantly. Incorporating the broth should take 15 to 20 minutes total.

When rice is mostly tender, but still has a very slight crunch, stir in hearts of palm and Parmesan cheese until incorporated; season with salt and pepper. Cook for 1 more minute to heat through, then stir in parsley and remaining 1 tablespoon butter.