Pat chicken breasts dry and season generously with salt, pepper, and oregano on both sides. If chicken breasts are very thick, consider pounding them slightly for more even cooking.

Heat olive oil in a large skillet over medium-high heat. Sear chicken breasts for 5-7 minutes per side, until golden brown and cooked through (internal temperature reaches 74 °C or 74 °C). Remove chicken from skillet and set aside.

Reduce heat to medium. Add minced garlic to the same skillet and sauté for about 1 minute until fragrant, scraping up any browned bits from the bottom of the pan.

Stir in the chopped sun-dried tomatoes and artichoke hearts. Cook for 2-3 minutes, allowing their flavors to meld with the garlic.

Pour in the chicken broth and heavy cream. Bring the mixture to a gentle simmer, stirring occasionally, and let it reduce slightly for about 5 minutes.

Stir in the grated Parmesan cheese, lemon juice, and fresh spinach. Continue to cook until the spinach has wilted and the cheese is melted into the sauce.

Return the seared chicken breasts to the skillet, nestling them into the sauce. Spoon some sauce over the chicken and let it simmer gently for another 5 minutes, or until the chicken is heated through.

Serve the chicken immediately, spooning generous amounts of the creamy Tuscan sauce over each piece.