In a bowl, combine olive oil, smoked paprika, garlic powder, onion powder, parsley, lemon juice, salt, and pepper. Coat your chicken breasts well and let them sit for at least 20 minutes. If you have the time, an hour is even better.

You want those flavors to sink in so the chicken stays juicy on the grill.

Heat up your grill pan or outdoor grill to medium-high heat. Add a little oil so the chicken does not stick. Grill each breast for about 5 to 7 minutes on each side, depending on thickness. You want it nicely charred with light grill marks.

You can use a thermometer. 165°F is perfect.

Place grilled chicken aside.

In a large skillet, heat butter and olive oil. Add onions and sauté until soft. Add garlic and cook until fragrant. Add your sliced portobello mushrooms and cook until they release moisture and soften.

Pour in the broth, heavy cream, Worcestershire sauce, thyme, Dijon mustard, salt, and pepper. Let it simmer on low heat for 10 minutes. If you want the sauce thicker, stir in the cornstarch mixture and simmer for 2 more minutes.

The sauce should be creamy, earthy, and rich.

Place the grilled chicken breasts in a baking dish or keep them on the skillet. Sprinkle jack cheese generously over the top. Pour some of the mushroom sauce over the chicken, then add another thin layer of cheese.

Cover for a minute so the cheese melts, or pop it into the oven for 2 minutes to melt everything beautifully.

Drizzle extra portobello mushroom sauce on top and garnish with fresh chopped parsley. Serve hot.