Dry chicken with paper towels and lightly season both sides of the chicken thighs with salt and pepper. Set the Instant Pot to “sauté”. Pour the olive oil and butter into the pot, swirling the butter until it melts. Using tongs, place the chicken thighs in the pot and brown chicken on each side, about 4-5 minutes per side (you may need to move chicken around so it doesn’t stick to the bottom of the pot). Remove from the pot, leaving the oil behind, and set aside. Add in the onion and garlic and stir frequently until the onions are softened and browned, about 3-4 minutes. Add 2 tablespoons of chicken broth to deglaze the pot, stirring and scraping the bottom of the pot to remove/dissolve the brown bits. Press “cancel” to turn off the Instant Pot. Stir in the orzo, lemon juice, zest, black pepper, salt, and remaining chicken broth, making sure to distribute the ingredients throughout the pot. Place the chicken thighs back into the pot with the other ingredients. Seal the Instant Pot and cook at high pressure (“manual” function) for 6 minutes. After it is ready, allow natural pressure release for at least 10 minutes before a quick pressure release to completely depressurize (until floating valve drops). Open the Instant Pot and remove the chicken thighs from the pot. OPTIONAL step: Place the chicken on a baking sheet lined with aluminum foil. Arrange the oven rack about 6-7 inches from the heat source and preheat the oven broiler. Broil the chicken until the skin crisps, about 2-4 minutes (check often). Stir the feta and spinach into the orzo. Taste for additional salt and pepper. Plate and top with more feta cheese if you like. Best served immediately.
One lemon equals around ¼ cup of juice and 1 tablespoon of zest. Add more or less depending on how lemony you like your orzo.