Trim roots and greens from radishes. Using a sharp knife or mandolin, cut the radishes into thin slices about 1/8″ thick. Set aside.
n a medium saucepan, add sugar, vinegar, lemon juice, thyme, chives and pepper. Cover and bring to a gentle simmer over medium-high heat.
Add radish slices and stir to ensure all slices are immersed in liquid. Reduce heat to medium, cover and simmer for 3 minutes. Remove pan from heat and set aside to cool for about 15 minutes.
After 15 minutes, drain the liquid from the radishes, remove thyme sprigs and put into a bowl to cool further. Once cooled, sprinkle with sea salt and garnish with chopped chives and black pepper as desired. Use as you would regular pickles – on sandwiches, salads, etc. Radishes will keep covered in the fridge for a few days