In a large bowl or directly in the slow cooker bowl, whisk miso paste, Worcestershire sauce and tomato paste into 5 cups warm vegetable broth until fully incorporated. This helps ensure the flavors are fully mixed into soup and there are no clumps.
Add all ingredients except for lasagna sheets and tofu ricotta to slow cooker pot.
Set slow cooker to 4 hours on high or 8 hours on low (8 hours makes a thicker, richer tasting sauce).
When lasagna soup has 20-25 minutes left to cook, break lasagna sheets into smaller pieces and stir well into soup (the smaller you break them, the less likely they are to stick together). Simmer noodles until al dente, about 20-30 minutes.
If desired, sprinkle vegan mozzarella shreds on top of the soup in last 10 minutes and allow to melt on top of lasagna soup just before serving.
Serve immediately while warm with a dollop of tofu ricotta, vegan mozzarella cheese shreds, nutritional yeast, red chili flakes, and fresh basil, if desired.
Instant Pot Instructions
In a large bowl or directly in the Instant Pot, whisk the miso paste, Worcestershire sauce and tomato paste into 4 cups warm vegan beef broth until fully incorporated. This helps ensure the flavors are fully mixed into soup and there are no clumps.
In the following order, add the ingredients to the Instant Pot: Vegan beef broth mixture, mushrooms, red lentils, spices, and crushed tomatoes. Do not mix.
Break lasagna sheets into thirds and layer on top of crushed tomatoes. Press them in slightly until just submerged. Again, do not mix.
Add the lid, and cook on manual high pressure for 6 minutes. Make sure the valve is set to seal.
Once Instant Pot has cooked at high pressure for 6 minutes, manually release pot pressure.
If desired, sprinkle vegan mozzarella shreds on top of the cooked soup and add the lid back on for 5-10 minutes to allow the cheese to melt.
Serve immediately with a dollop of tofu ricotta, nutritional yeast, red chili flakes, and fresh basil, if desired.
Storage
Once soup has cooled to room temperature, transfer to storage containers and store in refrigerator for 3-5 days.
How to Freeze
Freeze uncooked: Into a large gallon-sized freezer bag, add the dried basil, oregano, garlic powder, onion powder, vegan Worcestershire, sliced mushrooms, red lentils, tomato paste, and crushed tomatoes. Seal tightly, removing as much excess air as possible. Squish the ingredients around in sealed bag until combined. Freeze flat for up to 3 months. When ready to cook, dump contents of bag into the slow cooker frozen and add in 5 cups of broth. Add lasagna sheets with 30 minutes left to cook.
Notes
Lower sodium version: Vegan beef broth can be very salty, depending on the brand. If you are sensitive to sodium or prefer less salt, use 2-3 cups vegan beef broth, 1-2 cups water.
Adding vegan beef: I've made this lasagna soup before with an additional 12-16 ounces vegan ground beef. If doing so, brown the ground beef in 1 tablespoon of oil in a large skillet until cooked through and crispy before adding it to the slow cooker bowl.
Turn off slow cooker or Instant Pot immediately after cooking to prevent lasagna from overcooking.
If cooking in the Instant Pot, be sure to add the ingredients in the specific order listed. This is to prevent the lasagna, lentils and tomatoes from burning to the bottom of the pot.
I prefer making this soup in the slow cooker on low as it really allows the marinara to develop best flavor.