1Trim the greens and root ends from the radishes. Gently smash each radish with a meat mallet or the side of a knife until it cracks but stays mostly intact.
2Place in a bowl, sprinkle with 1 tbsp kosher salt, and toss to coat. Let sit for 30 minutes to draw out moisture.
3Rinse and drain well, then transfer the radishes to a large glass jar with a lid.
4In a small pot, combine the rice vinegar, water, sugar, soy sauce, garlic, sriracha, sesame oil, white pepper, and remaining 1 tsp kosher salt. Bring to a simmer over medium-high heat, stirring until the sugar dissolves. Remove from the heat and let cool slightly.
5Pour the brine over the radishes, cover, and refrigerate overnight.