Crock Pot Creamy Mushroom and Chicken Stew

Still looking for healthy recipes that can be made in the crock pot, I found this recipe from Laaloosh.

This recipe turned out okay, but I made a mistake on one crucial part of the recipe (which I will learn from) which made it another bumpy adventure. Edible but could have been better.

Ingredients
1 lb chicken breasts cut into bite-sized pieces
8oz baby Portabella mushrooms, sliced
1 onion (finely chopped)
1/2 cup carrots, chopped
1/2 cup fresh or frozen peas (I forgot to buy this, so I just skipped it)
2 stalks of celery (chopped)
1 packet powdered Mushroom Sauce seasoning mix (the original recipe call for one by Simply Organic. I couldn't find this anywhere so I used mushroom gravy mix)
2 cups fat free chicken broth
1 cup plain, non-fat Greek yogurt, at room temp (AT ROOM TEMP!!!! This is where I went wrong...)
3 cloves garlic, minced
1 tsp salt
1/2 tsp pepper

Directions:
Combine all ingredients EXCEPT the yogurt and place in crock pot.

Cook on low for 4-6 hrs.
Stir in (room temperature) yogurt, and warm until heated through, about 5 minutes.

I made the mistake of adding the yogurt before it was room temperature - huge mistake. It practically curdled in the stew. I ate some and it was tasty but looks wise it wasn't appealing. I also tried to freeze it... another misadventure.