In a large skillet or Dutch oven, melt the butter over medium heat.
Add the chopped onion and sauté until soft and golden, about 5-7 minutes.
While the onion cooks, thoroughly wash the spinach and remove any tough stems.
Add the clean spinach to the skillet with the onions.
Stir frequently until the spinach is completely wilted, which should only take a couple of minutes.
Transfer the cooked onion and spinach mixture to a large pot.
Pour in the broth.
Peel the cucumbers, slice them in half lengthwise, and use a spoon to scrape out the seeds.
Dice the cucumber flesh and add it to the pot.
Bring the mixture to a simmer and cook for about 20 minutes to soften the vegetables.
Carefully transfer the hot soup to a blender in batches.
Blend until the soup is completely puréed and silky smooth. Return the puréed soup to the pot.
Place the pot over low heat.
Add the sliced cream cheese and stir continuously until it has completely melted into the soup, creating a rich, creamy texture.
Stir in the pinch of nutmeg, hot paprika, and lemon juice.
Season generously with salt and pepper to your liking.
Remove the pot from the heat and stir in the light cream.
Transfer the soup to a container and chill in the refrigerator for at least 4 hours, or until completely cold.
Once chilled, taste the soup one last time and adjust the seasoning if necessary, as cold temperatures can dull flavors.
Ladle the cold soup into bowls.
Garnish with a sprinkle of sweet paprika for color, a dollop of sour cream, and a scattering of fresh dill, if desired.
Don't skip the final tasting! Flavors change and mellow as food chills, so you may need to add an extra pinch of salt or a squeeze of lemon juice just before serving to make it perfect.
