Preheat the oven to 400 degrees F.
Prepare two muffin tins, making a total of 24 pieces, by spraying them with cooking spray and lining each tin with parchment paper cups.
In a large skillet, heat olive oil over medium heat, and sauté the onion, garlic, salt, pepper, thyme, oregano, and red pepper flakes. Cook until the onion becomes tender, which should take around 5-6 minutes.
Add spinach to the pan and mix it with the onion mixture. Pour in Worcestershire sauce and chicken broth, ensuring everything is well combined. Cook until most of the liquid has reduced, and the mixture becomes solid. Remove the skillet from heat and allow it to cool to room temperature.
In a large bowl, combine the turkey, 3/4 cup of breadcrumbs, and egg. Mix the ingredients using your hands, then add the spinach mixture to the bowl and mix it all.
Spoon the combined mixture into the muffin tins, nearly filling each tin to the top. Gently smooth down the surface. Sprinkle the remaining bread crumbs on top and bake the muffins until they are cooked through and reach an internal temperature of 160 degrees F, which should take about 20-25 minutes.
Once they are done baking, remove the muffins from the oven and let them cool slightly before adding small mounds of mashed potato on top, either by piping or dolloping.