Cook red beans in Instant Pot, check the tenderness and reserve. They will cook very little more during simmering, so it's best if they are done to your taste in this step.
Heat olive oil in heavy pot or Dutch oven.
Add onion, bell pepper and celery. Cook, stirring occasionally, until onions are tender and bell peppers are becoming less green, about 5-6 minutes.
Stir in garlic and cook for about 1 minute.
Stir in Cajun seasoning until fragrant and the vegetables are coated, about 1 minute.
Mix in the tomato paste until it coats the vegetables.
Stir in stock, red beans, hot sauce, and bay leaf; Bring to a boil.
Tip: Usually I start cooking my rice at about this point.
Turn the heat to a simmer, cover the Dutch oven and simmer for 15 minutes. Uncover; continue to simmer until reduced, an additional 15 minutes. If the slow-cook setting seems not to be reducing the liquid enough, use the saute setting instead. When it’s on saute, be sure to stir every 15 minutes or so to prevent sticking.
Using a wooden spoon, mash beans until slightly thickened, if desired; season with salt, pepper and more hot sauce, to taste. Or if you have low-salt eaters as I do, place those items on the table.
Stir your cooked beef into one section of the bean mixture. I actually divide the half pound into two bowls and spoon the red beans on top, then stir.
Serve immediately over rice and garnished with parsley.