Cut the chicken in half lengthwise so you've got 2 thinner cutlets. Season each side with the garlic powder and lemon pepper. If the lemon pepper seasoning you're using doesn't contain salt, be sure to salt the chicken as well.
Add the oil and butter to a skillet over medium-high heat and let the pan heat up for a few minutes. Sear the chicken for about 5 minutes/side or until it's golden and cooked though. Transfer the chicken to a plate (tent with foil to keep warm if you wish).
Reduce the heat to medium and add the garlic to the skillet and cook for about 30 seconds.
Stir in the chicken broth and lemon juice and scrape up any brown bits from the bottom of the pan.
Add in the cream and gnocchi. Give it a good stir and ensure the gnocchi is submerged in the liquid. Let it bubble gently, uncovered, for 5-7 minutes, stirring occasionally, or until the gnocchi is cooked and the sauce has thickened. The gnocchi will release starch as it cooks, thickening up the sauce, so do not pre-cook the gnocchi. Keep in mind the sauce will thicken more as it cools, so don't let it get too thick (add a splash more broth if needed).
Take the pan off the heat and add in the parmesan cheese and spinach. Toss until the spinach has started to wilt and it's nicely mixed in. Add the chicken back into the skillet (along with any juices from the plate) and spoon some sauce over top. Serve immediately.