Set a large enameled dutch oven over medium-high heat. Add the olive oil and 1 tablespoon of butter.
Cut the chicken into bite sized pieces. Dust the chicken with a light coating of cornstarch, dried oregano, salt, and pepper. Sauté the chicken until it's golden brown. Remove the chicken from the pot, transfer it to a plate, and set it aside.
Next, add the other tablespoon of butter, diced onion, and minced garlic. Stir the onions well and cook for 3-4 minutes until they are slightly translucent.
Add the arborio rice and stir it well so the butter coats the rice completely. Toast the rice for 2-3 minutes.
Now it's time to add the half cup Marsala wine. Stir it in really well and bring it to a bubble.
After the wine as reduced, you can start adding the chicken stock about 1 cup at a time. Add a cup of warm chicken stock, stir it well, bring it to a boil and let the rice absorb the liquid. Reduce to medium heat if needed.
Repeat 3 times or until the rice is tender and cooked through.
When the rice is cooked through, you can add back the chicken and stir in the mascarpone cheese. Taste for seasoning and add salt or pepper if needed.
Stir it so it's well combined. Top with parmesan cheese and minced parsley.