Preheat and prep: Heat your oven to 400°F (200°C).
Lightly grease a 9x13-inch baking dish with olive oil.
Season the chicken: Pat the chicken dry. Season both sides with 1 teaspoon salt, 1/2 teaspoon black pepper, and half the oregano and dill. Add a light drizzle of olive oil.
Sauté the aromatics: In a skillet over medium heat, warm 1 tablespoon olive oil.
Add the onion or shallot and cook 2–3 minutes until softened. Stir in the garlic for 30 seconds until fragrant.
Wilt the spinach: Add fresh spinach to the skillet in batches. Toss until just wilted and bright green, 1–2 minutes.
If using frozen spinach, add it to the pan and heat through. Season lightly with salt and pepper.
Make the creamy base: In a bowl, whisk the cream (or Greek yogurt), softened cream cheese, remaining oregano and dill, lemon zest, and a squeeze of lemon juice. Add a pinch of red pepper flakes if you like.
Fold in half the feta and the spinach mixture until evenly combined.
Assemble the bake: Place the seasoned chicken in the prepared baking dish. Spread the spinach and feta mixture over the top, coating the chicken evenly. Sprinkle with the remaining feta and the Parmesan if using.
Bake: Bake uncovered for 22–28 minutes for breasts or 25–35 minutes for thighs, depending on thickness.
The chicken is done when the internal temperature reaches 165°F (74°C) and the top is lightly golden and bubbly.
Rest and finish: Let the dish rest for 5 minutes. Taste the sauce and brighten with another squeeze of lemon if needed. Finish with freshly ground pepper and a drizzle of olive oil.
Serve: Pair with rice, orzo, mashed potatoes, or crusty bread.
A crisp salad or roasted veggies make an easy side.