Heat a soup pot over medium-high heat. Add the bacon and render until crisp. Remove, finely chop and reserve the bacon bits.
Spoon off all but a few tablespoons of the smoky drippings and add the butter, to melt. Reduce the heat a bit, then add the potatoes and stir to coat. Add the parsnips, onion, garlic, black pepper, nutmeg and parsley; partially cover and cook to soften, 15-20 minutes, stirring occasionally. The color of vegetables should be light golden. Remove the parsley.
Puree the potatoes and parsnips, in batches if necessary, in a food processor or blender with the stock, or just add the stock to the soup pot and use an immersion blender. Stir in the cream and reserved bacon bits, then season the soup with salt, to taste.
Serve in shallow bowls with pepitas and chives to garnish, and toasted and buttered sourdough rolls or English muffins alongside for dunking.