At least 90 minutes before serving
Salt and pepper the brisket.
Heat oil in a pressure cooker over medium-high heat. Sear the brisket until browned on all sides. This can be done in batches if there isn't enough room in the pressure cooker. Remove the meat from the pressure cooker.
Add oil to the pressure cooker along with the onion, red pepper and carrots. Cook until softened, about 10 to 15 minutes. Add the brisket back to the pressure cooker, settling it into the vegetable mixture. Add the remaining Pressure Cooked Brisket ingredients.
Seal the pressure cooker, bring to full pressure (15 psi), and cook for 60 minutes.
While the brisket is cooking, you can make the cucumber salad and mixed vegetables.
After 60 minutes, remove the pressure cooker from the heat and let it depressurize naturally. Take the brisket out of the pressure cooker and pull it apart using a fork, or roughly chop it with a knife.
The brisket can be kept for several hours or in the refrigerator for several days.
At least 30 minutes before serving
Place some oil in a pan and heat over medium-high heat. Add the onion then salt and pepper it. Cook until it just starts to brown, about 10 to 15 minutes. Remove the onion from the heat and set aside.
Repeat the above process for the peppers, then the mushrooms.
This process can be done ahead of time and then reheated once the meat is done.
At least 20 minutes before serving
Combine the cucumbers with the other ingredients and mix well.
This can be done ahead of time and stored on the counter for an hour or two, or in the refrigerator for about 5 hours.
At least 10 minutes before serving
Take 500 grams of liquid and vegetables from the pressure cooker and combine them with the xanthan gum and Ultra-Sperse. Blend well using an immersion blender or standing blender. You can add more xanthan gum and/or Ultra-Sperse to thicken the sauce as much as you want. For a more traditional sauce you can blend in corn starch or flour and bring it to a boil.
The sauce can be kept for several hours or in the refrigerator for several days.
Combine the shredded beef with the mixed vegetables and a spoonful of the peppered beef sauce. If they have cooled off you can reheat them in a pan.
Add a good helping of freshly ground black pepper. Place the meat and vegetables on a plate next to the cucumber salad then serve.