While the squash roasts in the oven, prepare the filling. In a large skillet, heat the olive oil over medium heat. Add the onions, cinnamon, cumin, paprika and cayenne pepper and cook, stirring often until the onions become translucent, about 5 minutes.
Next, Stir in the garlic and cook, stirring; until aromatic, about a minute.
Stir in the ground meat and cook, crumbling the meat into smaller pieces with a wooden spoon, until the meat is cooked through, about 5-6 minutes for ground chicken. The cooking times for other proteins, plant-based proteins and grains can be found below on the Chef's tips section.
Lower the heat to medium-low, and stir in the broth and the tomato paste. Cook for about 1-2 minutes then, season with salt and pepper to taste. Keep warm.
Reduce the oven temperature to 375 degrees Fahrenheit and remove the acorn squash from the oven. Using a spoon, scrape about two tablespoons of flesh from the cavity of each squash (you should have about ½ cup altogether). Break up the scooped roasted squash into smaller pieces (try not to mash it into a purée. Uneven-sized pieces are fine)
Stir the scooped roasted squash pieces into the meat mixture, Mix until well combined. Next, stir in the pistachios, raisins, cranberries, mint and parsley. Toss to combine. Season to taste.