Mix all dry ingredients together in large mixing bowl
Add ground turkey to mixture
Add 1 beaten egg to mixture
Add "splashes" of seltzer until mixture is pasty; not too mushy but not too solid
Mix all ingredients together to incorporate
Test consistency of mixture with fingers, add eyeball amounts of additional seltzer or breadcrumbs/cheese to make softer or more firm
Form meatballs with either ice cream scooper or hands. If using scooper and the scoop part is small, overfill slightly. Mold each portion into an approximate ball.
Place meatballs on baking sheet lined with parchment paper
Place baking sheet in oven for 25 minutes, check with toothpick for "done-ness", should come up dry