Remove kernels from the cleaned cob. Place kernels in a blender and blend until smooth. Strain the pureed corn through a fine meshed sieve, pushing out as much juice out as possible.
In a heavy bottomed pot cook corn juice on medium heat. Stirring with a rubber spatula constantly to avoid scorching. Cook until the natural starches in the corn thicken the mixture–it should resemble a loose pudding. Put the thickened corn in a bowl. Place plastic wrap on top of mixture so a skin does not form. Chill mixture in refrigerator until cold.
Toast hazelnuts at 350° F for approximately 10 minutes or until golden. Cool nuts completely. Rough chop the toasted hazelnuts.
Divide the corm mixture between four small bowls. Sprinkle 1 teaspoon of chopped hazelnuts on half of each bowl. Place a quenelle of caviar on the opposite side of the hazelnuts. Place one tarragon leaf on top of the caviar.