Wash all the vegetables. Slice radishes and asparagus, making all the pieces more or less the same size. Slice off the end of the leeks then slice the white and light green part of the leeks, leaving the dark green ends.
Melt a few teaspoons of butter in a large heavy skillet over medium heat. Add the leeks and 1/2 cup stock. Simmer for 5 minutes. Season with a few pinches of salt, add the radishes and asparagus and simmer for 3 more minutes. Next, add the peas and radish greens, making sure there is enough liquid in the pan as you go and adding more stock if needed. Continue cooking until the peas are bright green and tender (a few minutes longer). The radish leaves will wilt and taste mils and slightly nutty.
When vegetables are done, remove from heat and add a heaping spoonful of ghee/ butter. Season with salt and stir in the tarragon and lemon juice. Taste and adjust seasonings.
Serve with a dollop of seasoned fresh yogurt and bread.