Bring a wide skillet or dutch oven to medium heat and drizzle with olive oil. Saute the chopped carrot, celery and shallot for 3-4 minutes until vegetables begin to soften. Add the garlic and continue sauteing for another minute.
Once done, remove the vegetables and set aside to cool slightly.
To a bowl, add the ground turkey, ground Italian sausage, sautéed vegetables, chopped herbs, eggs, Worcestershire sauce and panko breadcrumbs and season with salt and pepper.
Give the mixture a good mix so everything is combined well and form the mixture into golf ball sized meatballs.
To the same skillet, bring up to medium-high heat and add more olive oil if needed. Sear the meatballs on all sides until deeply charred. Do this in batches to not overcrowd the pan, if necessary, then remove and set aside.
Add butter to the pan and once melted, add the flour and whisk until the flour is cooked off.
Add the chicken stock and the fresh sage and whisk the mixture together, picking up any meaty bits from the bottom of the pan. Continue whisking until the gravy thickens.
Add the heavy cream and season with salt and pepper and taste for seasoning.
Add the seared turkey meatballs back into the gravy and continue simmering for 15-20 minutes until the meatballs are just cooked through.
Once done, garnish with additional thyme and serve the turkey meatballs with the creamy gravy on top.