Gather all ingredients before starting the recipe.
Melt butter in a medium sauce pan over medium heat. Add chopped onions and grated garlic and cover with a lid. Cook for 5-6 minutes of until the onions are soft. Do not brown.
Add 2 tablespoons of flour and stir to combine. Cook for 1-2 minutes, then add clam juice, stirring constantly with a wire whisk.
Add cream, milk, lemon juice, chopped thyme and chopped tarragon and season with kosher salt and Old Bay seasoning. Stir to combine.
Add diced potatoes and increase heat to bring to a simmer. Cook for 10-15 minutes or until potatoes are cooked. Stir periodically and scrape up the bits from the bottom to prevent clumping.