Lightly grill one side of the bread or toast it on one side in a toaster oven. Place the bread toasted side up on a large plate, spread with the fromage blanc, and season with salt and white pepper. Or whisk the cottage cheese and sour cream together vigorously (or, if you’d like a smoother blend, pulse them a few times in a mini processor or with a hand held blender), spread on the bread, and season.

Toss the cucumber and tomato cubes with salt and white pepper and spoon them over the tartine, paying no attention to what spills over onto the plate. Sprinkle with chives and a tiny pinch of herbes de Provence, if you’re using them. Leave the slice of bread whole or cut it in half; serve immediately.