Preheat oven to 375 degrees F.
Butter 8, ½ cup ramekins and coat well with breadcrumbs, knocking out excess and reserving.
In a medium saucepan, melt butter over moderately low heat and whisk in flour.
Cook roux, whisking constantly, for 3 minutes.
Add milk in a stream, whisking.
Bring to a boil and remove from heat.
In a large bowl, whisk together ¾ cup cheese, milk mixture, yolks, sun-dried tomatoes, dill, and season to taste (careful – the feta is already quite salty!).
Beat whites until they hold stiff peaks.
Stir half of whites into cheese mixture to lighten and fold in remainder, gently but thoroughly.
Fill each ramekin halfway with soufflé mixture and divide remaining cheese among ramekins.
Fill with remaining soufflé mixture and sprinkle with reserved crumbs.
Put ramekins in a large baking pan and add enough hot water to reach halfway up sides of ramekins.
Bake in middle of oven until golden-brown, about 25 minutes.
Remove and let stand in pan 15 minutes.
Run a knife around edge of soufflés and invert onto a baking sheet.
(may be prepared up to 1 ½ hours in advance and kept at room temperature, or cover with plastic wrap and refrigerate up to 6 hours, no more, bring to room temperature before continuing).
Preheat oven to 425 degrees F.
Bake in middle of oven until puffed and golden-brown, 5-7 minutes.
Divide salad among 8 salad plates and put one soufflé atop each plate of greens.