In Blender add:
1 cup milk or milk substitute (soy,etc)

30 grams protein powder : 1 scoop?***
1 TBSP dark cocoa powder (optional)
2 packet stevia or artificial sweetener

1 tsp cinnamon (fine if you leave out)
1/2 tsp vanilla(fine if you leave out)

Pinch of sea salt or regular salt

Thickeners:
1/3 tsp xanthan gum (thx acg!)**
1/2 tsp guar gum***
please read tips section

Blend away on high adding in a couple of cubes at a time - unless you have a monster blender.
Approximate amount of ice cubes (18 cubes : 220+ grams+?)

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Tips:
Thickeners:
Xanthan thickens the ice-cream, and guar gum makes it creamy. thin? add more xanthan, too icy? add more guar. Adding a few extra cubes may be required.. Also you may need to stop and stir a bit with a spoon this gets super thick but doesn't end up with an icy texture.

Protein Powder:
Also some protein powders have xanthan and guar gum in them which may change the requirement a bit. 
if your powder has it in it add the amounts in smaller amounts - you can end up with goop


Ideas:
Adding half of a frozen banana and or a frozen fruit is a nice touch !
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Another option is to use pasteurized egg whites and reduce the milk content, IE:
Typically I use this version..

1/2 Cup of Milk
1/2 Cup of Egg Whites
1 Tsp of White Vinegar (Optional)

You should end up with a nice soft serve portion of ice cream...
Photo is a bit dark but here's an example: