Preheat your oven to 400°F and line a baking sheet with parchment paper or foil. While the oven heats, chop the onion into small pieces, mince the garlic cloves, and roughly chop the spinach into 1/2-inch pieces. The grated carrots should already be finely shredded and ready to use. Having everything prepped and ready will make the assembly process smooth and quick.

Heat the vegetable oil in a skillet over medium heat. Add the chopped onion and cook for about 2 minutes until it softens slightly, then add the minced garlic and cook for another 30 seconds until fragrant. Add the grated carrots and chopped spinach, stirring occasionally, and cook for about 5 minutes until the spinach is wilted and any excess moisture has evaporated. I like to cook these vegetables first because it removes moisture from the spinach and develops deeper flavors through light caramelization, which keeps the meatloaf moist and flavorful rather than soggy.

While the vegetables cook, pour the milk into a bowl and add the Panko breadcrumbs, stirring to combine and allowing them to soak for 2-3 minutes. Once softened, stir in the egg, 1 tablespoon ketchup, 1 tablespoon balsamic vinegar, minced parsley, thyme, salt, pepper, and Worcestershire sauce until well combined into a thick paste. This wet binder mixture is what holds the meatloaf together and keeps it tender, so make sure everything is evenly distributed.

Transfer the sautéed vegetables from Step 2 to a large bowl and add the ground chicken. Pour the wet binder mixture from Step 3 over the chicken and vegetables, then gently mix with your hands until just combined—avoid overworking the mixture, as this will make the meatloaf dense and tough. Shape the mixture into a loaf on your prepared baking sheet, pressing it gently into a compact shape about 2 inches tall and 6-7 inches long.

Combine the 1/4 cup ketchup, 1.5 tablespoons balsamic vinegar, and smoked paprika in a small bowl, stirring until smooth. Brush this glaze evenly over the top of the shaped meatloaf. Place the baking sheet in the preheated 400°F oven and bake for 30-35 minutes, until the internal temperature reaches 160°F when measured with a meat thermometer in the thickest part of the loaf. The glaze will caramelize slightly and add a tangy-sweet crust to the outside.

Remove the meatloaf from the oven and let it rest on the baking sheet for 5-7 minutes before slicing. I find this resting time essential—it allows the juices to redistribute throughout the meatloaf, making each slice much more tender and moist. Slice with a sharp knife and serve warm.