How to Make It
In a large saucepan, combine the half-and-half with the Parmigiano-Reggiano rind and garlic and bring to a simmer. Cover and let stand off the heat for 1 hour. Strain and discard the solids. Return the half-and-half to the saucepan.
Meanwhile, preheat the oven to 450°. Brush the cut sides of the eggplants with the olive oil and place cut side down on a parchment paper–lined baking sheet. Bake for about 45 minutes, or until tender.
Scoop the eggplant flesh into a blender and puree until smooth. Strain the puree through a fine sieve into the saucepan with the cream. Stir in the lemon juice and peas and season with salt. Heat until warmed through, about 5 minutes. Ladle the soup into cups, top with the radishes and preserved lemon peel and serve.