• Cut the damaged or wilted dark green parts of the leek and the root off and discard. Slice leeks on half, lengthwise, and rinse in between the layers. (There is often dirt hiding between the layers of the leek.)
• Cut off the darker green shoots off the fennel bulb and discard. Slice fennel bulb in half.
• Cut celery and carrots in halves of quarters so it fits better in a pot.
• Peel the outer loose skin off the garlic bulb and slice off the very tip of the bulb, exposing the "meat" of garlic.
• Preheat a large Dutch oven or another large soup pot over medium-high heat to sear the vegetables.
• Sear vegetables in batches so you don't overcrowd the bottom of the pot until golden brown. When all the vegetables have been seared, add them back into the pot. (Sear the bulb of garlic cut side down.)
• Pour in water and stir in herbs, salt, peppercorns, and tomato paste until completely incorporated.
• Bring everything to simmer and lower the heat to low. Cover with a lid but leave a small crack for the steam to escape.
• Let the vegetables cook for about an hour.
• Cover the strainer with a mesh vegetable bag or cheese cloth and strain the stock through it.
• Let the cooked vegetables cool in the strainer for a little while and then squeeze out leftover liquid out of them through the mesh bag (or the cheese cloth).
• Discard the cooked vegetables.

Storing:

• Store homemade vegetable stock in the refrigerator, in glass jars with a lid. In the refrigerator, homemade stock will last for up to 3 days. I always recommend using the stock within a day or two or freeze it.