Set Instant Pot to saute. When hot, spray inner liner with cooking oil spray, then add in onions, celery, carrots and saute for 1-2 minutes or until fragrant and slightly translucent. Add in garlic and saute for an additional minute.
Add in chicken and sprinkle with salt and pepper. Pour stock or broth over the veggies and chicken, then place the head of cauliflower on top.
Lock lid and set IP for 15 minutes on manual. (Set for 20 minutes if using a large block of frozen chicken)
Now, make the dumplings. Start by adding the gluten free flour, salt, and baking powder to a mixing bowl. Use a fork to whisk the dry ingredients together. Next, add the chives (optional), milk, and melted butter to the dry ingredients and stir until well combined and you have a sticky dough.
After cook time, let the pot naturally release for 5 minutes, then quick release the rest of the pressure. Remove lid and place pot on saute to keep the soup hot.
Remove cauliflower from the Instant Pot and place in a blender with milk and a few tablespoons of broth. Blend until creamy and smooth.
Remove chicken, shred, then return to the pot. Add cauliflower puree back into the pot.
Using a teaspoon, drop spoonfuls of dumpling dough into the pot, trying to work around the pot so the dough doesn’t stick together. After all of the dumplings have been added, place lid back on the IP and set for zero minutes. After cooktime, do a quick release.
Stir in 2 tsp butter. Taste and adjust seasonings, if necessary. Garnish with fresh herbs, if desired.