Coat the Chicken: Dredge the chicken fillets in the seasoned flour mixture on both sides, ensuring an even coating. Set aside.
Sauté the Chicken: Set the Instant Pot to Sauté mode on High/More. Add olive oil and 2 tbsp butter, allowing it to melt for about 3 minutes.
Sear the Chicken: In batches, sear each piece for about 1 minute per side until lightly browned. Remove and set aside on a plate.
Prepare the Aromatics: Add the remaining 2 tbsp butter to the Instant Pot. Scrape up any browned bits. Stir in shallots and sauté for 2 minutes until they start to brown. Add the minced garlic and cook for 1 minute more. Pour in the white wine and lemon juice, bringing it to a simmer.
Add Seasonings & Broth: Pour in the chicken broth, oregano, salt, and black pepper, stirring well to deglaze the pot. Return the seared chicken to the Instant Pot.
Pressure Cook: Secure the lid, set the valve to sealing, and select Manual/Pressure Cook on High for 5 minutes. Once done, quick release the pressure and preheat the oven broiler.
Make a Slurry: In a small bowl, mix cornstarch with 1 tbsp water to create a slurry. Set aside.
Thicken the Sauce: Transfer the cooked chicken to a casserole dish. Set the Instant Pot back to Sauté mode on High. When the sauce begins bubbling, stir in the cornstarch slurry for 30 seconds until it thickens. Turn off the Instant Pot and stir in the artichoke hearts. Pour the sauce over the chicken in the casserole dish.
Broil the Topping: In a small bowl, mix breadcrumbs and Parmesan cheese. Sprinkle the mixture evenly over the chicken and add a few extra shakes of oregano. Place the casserole under the broiler for 2-3 minutes, watching closely to prevent burning.
Serve: Remove from the oven and serve immediately over rice or angel-hair pasta. Enjoy with crusty Italian or French bread for dipping in the flavorful sauce.