Stir together ground turkey, egg, panko, salt, 1 teaspoon garlic, and ¼ teaspoon pepper in a medium bowl until evenly combined. Shape mixture into 12 (about 1 ½-inch) meatballs; transfer to a parchment paper–lined baking sheet. Cover and refrigerate until ready to cook.

Cook bacon in a large skillet over medium-high, stirring often, until crisp and rendered, about 8 minutes. Transfer bacon to a paper towel–lined plate using a slotted spoon. Reserve ¼ cup drippings in skillet; discard remaining drippings, or reserve for another use.

Return skillet with drippings to medium-high. Cook meatballs, turning occasionally, until browned on all sides, about 6 minutes. Transfer meatballs to a plate, and set aside.

Add mushrooms to skillet with drippings, and cook over medium-high, undisturbed, until browned on 1 side, about 3 minutes; stir and cook 2 more minutes. Add onion, 2 tablespoons broth, and remaining 2 teaspoons garlic. Cook, scraping up browned bits from the bottom of the skillet, until onion is just tender, about 3 minutes. Add flour; cook, stirring constantly, for 1 minute. Add wine, mustard, thyme, and remaining ½ cup broth; bring to a boil over medium-high.

Add meatballs and half of reserved bacon to skillet; simmer over medium-low, turning meatballs often, until a thermometer inserted into meatballs registers 165°F and sauce is thickened, 8 to 10 minutes. Stir in cream and remaining ¼ teaspoon pepper. Season to taste with salt. Sprinkle with remaining bacon, and garnish with additional thyme leaves.