Preheat your oven to 400°F.

Heat a large skillet over medium heat and add the olive oil.

Place the chicken breasts in the skillet and cook for about 8 minutes, flipping halfway through, until fully cooked and no longer pink inside. Remove from heat.

In a mixing bowl, combine the biscuit mix with the cold water, shredded cheddar cheese, and green onions. Stir until just combined and set aside.

Lightly grease a 9×13-inch baking dish with cooking spray. Spread the marinara sauce evenly across the bottom.

Place the cooked chicken breasts on top of the marinara sauce.

Spoon the biscuit mixture over the chicken and gently spread it out to cover the surface evenly.

Bake for 25 minutes or until the top is golden brown.

While the casserole is baking, mix the melted butter with the seasoning packet from the biscuit mix.

After removing the casserole from the oven, brush the butter mixture over the top.

Let rest for 5–10 minutes before serving warm.