"How to help 11-mth-old chew his food?"

It's awesome that you notice that his food isn't being fully digested.  If his body isn't fully breaking the food down, it means it's not reaping the full nutritional benefits it could.  Good eye, mom!

I don't know about pureeing the food, but definitely keep the pieces super-small.  I'm talking smaller-than-diced silly-small.  His mouth is still producing more saliva that ours does, and the enzymes in his spit will jump-start the process necessary to break down the food.  If you make sure the pieces are super-small, you're doing the chewing for him...chewing only grinds food into small pieces, right?

Also, if "he likes to stuff the food in his mouth," I recommend giving him his food in smaller portions at a time.  So give him about 1/4 of a cup, let him eat it, then another 1/4 cup.  This will force him to take smaller bites, which will allow the saliva to work better.

If all else fails, talk to your pediatrician.  She may be able to recommend foods that promote the digestive system, or (absolute worst case scenario and very unlikely) you may find that his stomach isn't producing enough hydrochloric acid.

His body can absorb the nutrients without making the food into mush. His system isn't failing if the food leaves his body whole.

Without teeth, he is likely only going to be able mash the food with his tongue. If he is happy to have some texture in his food, then let him have it. For a lot of kids texture bothers them so it's hard to get them to try new foods, he is better off because he likes food with texture. Keep feeding him both, maybe mix the whole pieces in with the pureed food so he gets both. But there is absolutely nothing wrong with the food coming out whole in his diaper.

I would make sure that you puree his basic needs food, so he’s getting everything he needs. Nutrient dense foods might be yogurt, scrambled eggs, tofu, carrots, refried beans, avacado, peanut butter etc. Thereafter, the extra snacks let him continue to try to chew them. He may have better success with more quickly dissolving foods made for babies such as those cereal puffs, teething cookies, etc.

FYI: some food should come out whole, corn for example or bean husks. However, your baby should not be passing whole carrots or peas. Make sure he's not stuffing them in his diaper lol! I would suggest asking your doctor about this if your seeing cooked veggies not digesting well.

Its not hurting his digestive system, he should still be getting most of his nutrition from formula and not from baby food at this point since he is under a year, food is more of an educational experience at this point. Im wondering why you are feeding him foods he cant break down, whats wrong with baby food if he has no teeth. I also feed my grandson those puffs that break down but he mostly eats baby food and formula. He is 8 months old and has 4 teeth.

I would feed him baby food thats not chunky for the most part, with a few chewy snacks to help him learn how to eat.