Slice the garlic scapes; your 3/4 pound will give about 3 cups sliced scapes. Trim the root and green part of the green garlic, and remove the outermost layers, then chop it finely. **If you don’t have green garlic, mince 3 cloves ordinary garlic, and later in the cooking time, toss in a nice handful of arugula or spinach to enhance the green color.
In a medium to large saucepan, melt butter over medium-high heat. Add green garlic (or ordinary minced garlic) and sauté until translucent, about 3 minutes. Add the sliced garlic scapes, thyme, salt and pepper, and sauté for 5 minutes.
Stir in diced potato and broth, reduce heat to medium, and simmer until scapes and potatoes are tender, about 20 minutes. If you’re amping up the green color, then toward the end of this 20 minutes, add arugula or spinach.
When the potatoes are tender and any greens are wilted, add half-and-half, and purée the soup. I find that a high speed blender (Vitamix or similar) will give the most velvety texture, but an immersion blender or traditional blender will do, as long as you’re careful with hot liquids.
Stir in the lemon juice and season with more salt and pepper. Garnish with nutmeg and thyme sprigs, and serve hot.