Spinach Stuffed Chicken Breast with Sun-Dried Tomatoes and Mozzarella

Spinach stuffed chicken breast made with oil-packed sun-dried tomatoes, fresh mozzarella, and baby spinach. Seared golden in a cast iron skillet and finished in the oven in just 30 minutes. The sear-then-bake method is what keeps the inside perfectly juicy and gives the outside that deep golden crust that makes this look and taste like something you ordered at a restaurant. No dry chicken, no complicated steps, no special equipment beyond a skillet.

Key Ingredients To Make Spinach Stuffed Chicken Breast

All ingredients and their amounts are listed in the recipe card at the bottom of this post.

Boneless, skinless chicken breasts: The size of your chicken breasts matters more in this recipe than in most. I look for breasts that are around 6 to 8 oz each and similar in thickness. If they are too thin, you cannot cut a proper pocket without splitting the breast in half and the filling has nowhere to sit. If yours are on the thinner side, cover them with plastic wrap and pound them gently to an even thickness before slicing the pocket. Uniform size also means all four breasts finish cooking at the same time, so nobody ends up with a dry piece.

Sun-dried tomatoes (oil-packed, chopped): I always reach for the jarred variety packed in olive oil. They are already soft, deeply flavored, and ready to use straight from the jar with no soaking or rehydrating needed. I drain off the excess oil before stuffing so the filling does not turn greasy inside the pocket. The dry-packed variety does not work as well here because the short cook time is not long enough to fully soften them. The concentrated, almost jammy flavor of oil-packed sun-dried tomatoes is what makes this filling taste so rich without any extra effort.

Pro Tip: Reserve a teaspoon of the oil from the jar and brush it over the outside of the chicken before searing. It adds a subtle depth to the crust that plain olive oil alone does not give you.

Fresh mozzarella: This is the one ingredient I would really encourage you not to swap for a bag of pre-shredded cheese. Fresh mozzarella melts completely differently. It goes creamy and stretchy and coats everything inside the pocket when the chicken is sliced open. Pre-shredded cheese contains anti-caking agents that make it oily rather than melty. Buy fresh mozzarella in ball or log form and slice it yourself. About two generous slices per breast is the right amount. I have tested this with provolone and with cream cheese. Provolone melts nicely and has a slightly sharper flavor. Cream cheese makes the filling richer and creamier, almost like a warm dip inside the chicken. Both work too.

Fresh baby spinach: A small loose handful per breast is all you need. I do not wilt it beforehand because it wilts completely in the oven and folds right into the filling on its own. Baby spinach has a milder, slightly sweeter flavor than mature spinach and will not make the filling taste bitter. If you only have frozen spinach, thaw it completely and squeeze out every drop of moisture with a clean kitchen towel before using. Wet spinach turns the filling watery and causes leaking at the seams. Baby spinach, arugula, or Swiss chard works for this recipe too.

Extra virgin olive oil: Just one tablespoon for searing. You want the pan hot and the oil shimmering before the chicken goes in. Avocado oil works equally well if that is what you have on hand.

How to Make This Spinach Stuffed Chicken Breast

Preheat your oven to 350°F (177°C) and have your cast iron skillet or oven-safe pan ready on the stovetop.

1. Cut the pocket. I place one chicken breast flat on my cutting board and hold it steady with my non-dominant hand pressing gently on top. Using a sharp chef’s knife, I insert the blade into the thickest side edge of the breast, not the top and not the bottom, but the thick side, and I slice horizontally about three-quarters of the way through, leaving the opposite side intact. The goal is a pocket with three closed sides and one opening. A slow, deliberate cut gives you a clean pocket. Rushing this step is how breasts end up split in half. I repeat with all the chicken breasts before moving on.

2. Season inside and out. I season each breast generously with salt and pepper on the outside and inside the pocket. I reach my fingers in and make sure the seasoning coats the interior walls. This step is easy to skip and it makes a bigger difference than you would expect once all the ingredients come together in the oven.

3. Build the filling. I layer the filling into each pocket in this order: sun-dried tomatoes first, then mozzarella, then spinach on top. The order matters here. The tomatoes go deepest because they need the most heat to release their flavor fully. The mozzarella goes in the middle where it melts and acts as a kind of glue that holds the filling together. The spinach goes in last because it wilts with almost no heat and just needs to be in the pocket. Do not overstuff. The pocket should feel comfortably full, not straining at the opening.

4. Seal with toothpicks. I close the opening and run 1 to 2 toothpicks along the edge, angled slightly inward so they grip the meat on both sides of the seam. They do not need to be evenly spaced. They just need to keep the pocket shut through the sear so the filling stays where it belongs.

Pro tip: Toothpicks inserted straight across the opening tend to pull out during the sear. Angling them inward at about 45 degrees gives them more grip on the meat and keeps the pocket sealed through the whole cook.

5. Sear in a very hot skillet. I add the olive oil to my cast iron skillet over high heat and let it get genuinely hot, about 2 to 3 minutes. The oil should be shimmering before the chicken goes in. If the pan is not hot enough, the chicken steams instead of sears and you lose the crust entirely. I add the stuffed breasts and leave them completely undisturbed for 2 minutes. I do not move them, do not press down on them, and do not check the color underneath every 30 seconds. I let the crust form on its own, then flip and sear the other side for another 2 minutes. I am looking for a deep golden-brown color on both sides, not just a light tan.

6. Bake until the internal temperature hits 165°F. I transfer the skillet directly into the preheated oven and bake for 18 to 20 minutes. The only reliable way to know the chicken is done is a meat thermometer inserted into the thickest part of the breast, not into the filling. I start checking at the 18-minute mark because stuffed chicken can go from perfectly cooked to dry in just a few extra minutes. I pull them out the moment the thermometer reads 165°F (74°C).

7. Rest for 10 minutes before slicing. I take the pan out of the oven and let the chicken rest for a full 10 minutes before cutting into it. This is not optional if you want juicy chicken. Resting lets the juices redistribute back through the meat instead of running out onto the cutting board the moment you slice. I use those 10 minutes to remove the toothpicks, plate the sides, and get everything ready to serve. Then I slice each breast crosswise to show the filling and bring it straight to the table.