How to Make It
In a medium pot fitted with a steamer basket, steam the corn until tender, 15 minutes. Let cool, then cut the kernels from the cobs (you should have 1 1/2 cups); discard the cobs. Transfer the kernels to a blender.
Meanwhile, in a heatproof medium bowl, sprinkle the gelatin over ¼ cup of the milk. Let stand for 5 minutes.
In a small skillet, combine the remaining 1/2 cup plus 1 tablespoon of milk with the cream, salt and both sugars and bring to a bare simmer, whisking to dissolve the sugars. Scrape the hot milk mixture into the gelatin and stir until the gelatin dissolves. Pour the mixture into the blender over the corn and puree until smooth.
Strain the puree through a sieve into a large bowl, pressing on the solids; discard the solids. Strain again without pressing; discard any solids in the sieve. Set the panna cotta in an ice bath until cool, stirring occasionally. Scrape the panna cotta into four 8-ounce ramekins. Cover and refrigerate overnight until firm.
In a large bowl, combine all of the ingredients and mix until the sugar is dissolved. Let stand for at least 30 minutes, stirring occasionally. Serve the panna cotta in the ramekins with the compote.