Peel and dice the potatoes into roughly 1-inch cubes so they cook evenly. Slice the white and light green parts of the leeks into thin rounds, then rinse in a bowl of cold water and lift out to remove grit. Finely chop the onion and mince the garlic.

Sweat aromatics

In a large heavy-bottomed pot over medium heat, melt the butter. Add the chopped onion and sliced leeks. Cook, stirring occasionally, until softened and translucent (about 6–8 minutes). Add the minced garlic and cook 30–60 seconds until fragrant, taking care not to brown.

Add potatoes and liquid

Add the diced potatoes to the pot and stir to combine with the leeks and onion for 1–2 minutes. Pour in the stock, add the bay leaf and thyme, and bring to a gentle boil. Reduce heat to a simmer, cover partially, and cook until potatoes are very tender, about 15–20 minutes.

Blend to desired texture

Remove and discard the bay leaf. For a smooth soup: use an immersion blender to puree the soup directly in the pot until silky. For a chunkier texture: transfer half the soup to a blender, puree until smooth, then return to the pot and stir to combine. Adjust texture with additional stock or milk if too thick.

Finish with milk and cream

Over low heat, stir in the milk and heavy cream (if using) until warmed through—do not boil. Taste and proceed to seasoning step.

Aromatics & Seasoning

While the potatoes simmer, season with salt, pepper, and grated nutmeg (if using). Start with the listed amounts, then adjust to taste after finishing the soup. If soup tastes flat after blending, a pinch more salt or a squeeze of lemon juice brightens the flavor.

Finishing & Garnish

Ladle the soup into bowls. Sprinkle chopped chives or green onion and the optional crumbled bacon or smoked salmon on top. Drizzle each bowl with a little olive oil or melted butter for shine and extra richness. Serve immediately.