In a small nonreactive dish, stir together the salmon roe and smoked olive oil. Set aside to infuse the roe with smoky flavor.
Place the cauliflower florets in a large pot with the onion, thyme sprigs and milk. Slowly bring to a boil over medium-high heat. Season with kosher salt, cover and simmer for 25 to 30 minutes, until the cauliflower is soft. Discard the lemon thyme sprigs. Transfer the cauliflower mixture to a blender and puree until completely smooth. Taste and season with salt.
Fill a medium saucepan with 2 to 3 inches of olive oil. Heat to 350 degrees F. Fry the Brussels sprout leaves a few at a time for 30 to 40 seconds, until browned. Drain on paper towels and season with fleur de sel.
To serve, ladle the soup into shallow bowls or small shot glasses or espresso cups and garnish with the fried Brussels sprout leaves. Sprinkle with the chives, smoky salmon roe and lemon thyme, and season with fleur de sel, cracked black pepper and more smoked olive oil.
When blending hot liquids, first let cool for 5 minutes or so, then transfer to a blender, filling only halfway. Put the lid on, leaving one corner open; Cover the lid with a kitchen towel to catch splatters and pulse until smooth.
Photographs by Yunhee Kim
Recipe courtesy Tyler Florence for Food Network Magazine