In a large nonstick skillet over medium-high heat, brown turkey and onions, stirring to crumble (or use my favorite crumbling tool), about 5-7 minutes. Drain if needed (if using very lean turkey, there probably won't be any need to drain.)
Transfer turkey and onion mixture to slow cooker. (This small, 3-quart slow cooker is the perfect size, but a 5- or 6-quart slow cooker will also work.) Add all other ingredients (except optional toppings) to slow cooker and stir to combine.
Cook on high (about 4-5 hours) or on low (about 6-8 hours).
Serve with optional toppings as desired.
Ketchup: We recommend purchasing natural or organic brands of ketchup whenever possible, in order to avoid brands that have high-fructose corn syrup and other "questionable" ingredients.
Alternate stovetop directions: Brown turkey and onions in a large pot over medium-high heat, stirring to crumble and draining if needed, as directed above. Instead of transferring the turkey and onion mixture to a slow cooker, leave the mixture in the large stovetop pot and add in all other ingredients (except optional toppings). Bring to a simmer and continue to simmer, covered, for about 30 minutes.
Freezing and make-ahead: This chili reheats beautifully, and like most chili recipes, its flavors are just as good if not even better after a day or two. It also freezes well if you want to make batches further in advance for freezer meal prep.