2. Make the Filling In a small bowl, mix the brown sugar, softened butter, cinnamon, and vanilla until it forms a thick, spreadable paste. It won’t look perfectly smooth, and that’s completely normal.
3. Stuff & Wrap Divide the mixture evenly and pack it firmly into each cored apple. Place each apple in the center of a 12×12-inch piece of heavy-duty aluminum foil. Fold the foil up and around the apple, sealing the edges tightly to create a snug little packet. Make sure there are no gaps—trapped steam is what makes these melt-in-your-mouth tender.
4. Slow Cook to Perfection Place the foil packets seam-side up in your slow cooker. You can stack them gently if needed, but avoid pressing too hard. Cover and cook on LOW for 4–5 hours, or HIGH for 2–3 hours. They’re done when a fork slides into the thickest part with zero resistance.
5. Serve Warm Let the packets rest for 5 minutes before opening (hot steam will escape!). Carefully transfer each apple to a bowl or plate, spoon any leftover syrup from the foil over the top, and dig in while they’re glowing hot.
