Chop leeks and wash thoroughly.

Peel and cut carrots into 2-inch pieces.

Peel and cut celery root into 1/2-inch pieces.

Combine leeks, carrots, celery root, parsley leaves and stems, dried minced onions, and kosher salt in a food processor.

Process until the mixture forms a fine paste, scraping down the sides of the bowl frequently (3-4 minutes).

Add tomato paste to the food processor.

Process for 1 minute, scraping down the sides of the bowl every 20 seconds.

Add soy sauce to the food processor.

Process for 1 minute.

Transfer the mixture to an airtight container.

Tap the container firmly on the counter to remove any air bubbles.

Press a small piece of parchment paper against the surface of the mixture.

Cover the container.

Freeze for up to 6 months.

To make broth, use 1 tablespoon of the base to 1 cup of boiling water.

Strain the broth if a particle-free broth is desired.