Take a soup pot and put it on the stove over medium heat. Melt butter in the pot.
Add celery, onion, garlic, and leeks to the melted butter in the pot. Cook and stir the mixture frequently for about 2-3 minutes.
Remove the pot from heat and add flour to the celery, onion, garlic, and leeks mixture. Mix everything together thoroughly.
Next, pour milk into the pot and start whisking the mixture vigorously.
Drain the clams and add the clam juice to the soup in the pot.
Place the pot on the stove again and slowly start heating the soup mixture. Keep stirring it often until it comes to a boil.
Once the soup comes to a boil, reduce the heat to a simmer. Add diced potatoes and seasonings, and let the mixture simmer for around 8-10 minutes.
Add the clams to the pot. Let everything simmer together for another 5 to 7 minutes.
Finally, add a dash of heavy cream to the soup pot, and stir it well. This will give your soup a creamy texture and rich flavor.
Your delicious clam chowder is now ready to be served. Enjoy!