Call your nutritionist before changing your diet. I had 2 weeks of full liquids. What got me through was using the unflavored protein powder and adding it to broth or soup with no chunky bits. I was able to still meet my protein needs and stay on track. It was a welcome change from milk based, sweet shakes.
Mash potatoes were allowed on the soft food stage, but I never ate them since it's all carbs, no protein. I could only eat 2 ounces so I wanted to make sure every bite counted.
Which unflavored protein powder did you use? I'm researching for my surgery in July.