How to Make It
Peel 2 clementines. Separate into segments. Make a decorative ice block by filling a Bundt pan or quart-sized container half full with distilled water; add segments. Freeze for 4 hours or until solid.
Peel remaining clementines with a serrated vegetable peeler, being careful to avoid white pith. Combine clementine peels and sugar in a large bowl; muddle sugar and peels with a muddler or wooden spoon until the sugar is infused with the oils from the peels. Let stand at room temperature for at least 90 minutes.
Juice clementines to equal 1 cup. Add clementine juice to peels and sugar; stir until sugar dissolves. Strain through a sieve over a punch bowl; discard peels. Add brandy and sherry to punch bowl; stir well.
Unmold ice block; gently place in punch bowl. Add cava, and stir gently. Grate a small amount of nutmeg over the punch.