Heat a frying pan or skillet over medium heat.
Add the walnuts and toast for about 4 minutes, until they darken slightly and smell fragrant.
Remove the walnuts from the pan and let them cool slightly, then chop them.
Place the sliced radishes in a large bowl.
In a small bowl, whisk together the olive oil, lemon juice, salt, and honey.
Pour the dressing over the radishes and toss until evenly coated.
Stack the mint leaves in layers, roll them up tightly, and slice crosswise into thin ribbons.
Add the mint ribbons and chopped walnuts to the radishes, and toss gently to combine.
Serve as is.