Mix ground chicken, panko, egg, garlic, Parmesan, parsley, salt, and pepper until combined, then roll into 1.5-inch balls.
Heat olive oil in a large skillet over medium-high heat and brown meatballs on all sides, about 6-8 minutes total.
Remove meatballs and reduce heat to medium.
Add butter, lemon juice, chicken broth, and thyme to the skillet and stir, scraping up any browned bits.
Return meatballs to the pan and simmer 3-4 minutes until cooked through and coated in sauce.
Transfer to a platter and spoon remaining sauce over top.