Add the chicken breast to the bottom of the crock pot. Pour the broth on top, then season the chicken with salt, pepper, garlic powder, thyme, and sage.
1 1/2 lb boneless skinless chicken breast, 1/2 cup chicken broth, Pinch of black pepper, 1 teaspoon garlic powder, 2 teaspoons dried thyme, 1 teaspoon dried chopped sage
Using a hand blender or countertop blender, blend the cottage cheese and chicken bouillon paste until smooth. Pour it over the chicken. Add the frozen vegetables on top.
24 oz full-fat small curd cottage cheese, 2 teaspoons chicken bouillon paste, 12 oz frozen mixed vegetables
Close the lid and cook on low for 6 hours, until the chicken is tender and shreds easily. Do not cook on high, the cottage cheese can curdle. If it looks slightly separated, that's okay, it will smooth out as you shred the chicken and thicken it.
When it's done cooking, preheat the oven to 400 degrees and remove the top oven rack, or make sure there's enough room for the crock pot insert to fit.
Use two forks to shred the chicken and stir the pot pie together to thicken. Dissolve the cornstarch in a small bowl with 1 to 2 Tablespoons of water to make a slurry. Stir it into the pot pie and turn the slow cooker to high heat. Let it cook and thicken for 3 to 4 minutes while you cut the topping. Give it a good stir and add up to 1 more Tablespoon of cornstarch if needed, keeping in mind it will thicken slightly as it cools.
2 Tablespoons cornstarch
Top the pot pie with the puff pastry pieces so they overlap and no filling shows through. Brush the entire top with the whisked egg.
1 package puff pastry, 1 egg
Using oven mitts, carefully remove the insert from the crock pot's outer shell and transfer it to the preheated oven. Bake for 15 to 17 minutes, until puffed and golden. Broil for the last 3 to 4 minutes if needed.
Garnish with flaky salt, fresh thyme, and black pepper. Serve right away.