Seal the meat: Heat oil in a pressure cooker. Add beef muscle pieces without seasoning and seal them by browning on all sides until the water released evaporates.
Add seasoning and aromatics: Add black pepper, generous salt, minced garlic, chopped onion, chili peppers (optional for spice), allspice, and a small spoonful of tomato paste. Stir well.
Add water and cook meat: Add enough water to cover the meat. Stir to loosen any browned bits from the pan. Seal the pressure cooker and cook under pressure for 15 minutes.
Prepare potatoes: After releasing pressure, add cubed potatoes to the broth. Add more water if needed to cover. Seal the pressure cooker again and cook for another 15 minutes until potatoes are tender.
Sauté calabresa sausage and kale: While potatoes cook, sauté sliced calabresa sausage in a pan without additional oil, letting it release its fat. Add black pepper, remaining onion, and allspice. Add thinly sliced kale and cook briefly until just wilted.
Blend the broth: Use an immersion blender or regular blender to blend the broth and potatoes until creamy but leaving some small potato pieces for texture.
Combine and finish: Add the sautéed calabresa and kale to the blended broth. Stir in chopped fresh coriander. Adjust salt if necessary.
Serve: Serve hot, optionally with bread, enjoying the creamy, flavorful caldo verde.