The new oat flour porridge method: mix 1/4 cup oat flour with 5 ounces milk, microwave for 55 seconds, and this is the key part, STIR IMMEDIATELY after cooking to integrate the mixture. Without immediate stirring the result will be a chunky mess, precisely the problem this process is intended to avoid. After mixing the porridge, both 32 grams of peanut butter and 1/4 cup of applesauce can be added and thoroughly mixed. Then, to finish the shake, the remainder of the milk is gradually mixed with 1/2 serving protein powder, then the oat/PB/applesauce porridge is added and mixed. The result is a smoother, tastier protein shake, although warmer from the microwave.
EDIT 2019-10-21_0816: For the oat porridge, 44 seconds in microwave, whisk thoroughly, then another 21 seconds and whisk again. Even better result! Tomorrow will try 30 seconds, whisk, then 30 seconds and whisk again.