Here are some great ways to finish steamed haricots verts or other slender green beans.
First idea: saute them in butter, then add toasted sliced almonds. You can amp the flavor even more by using brown butter, or even bacon fat.
Next: haricots verts with shallots. Slice and brown a couple handfuls of shallots in butter, then add some white wine or sake and the haricots verts.
Or, try this nifty variant: roast plum or cherry tomatoes with olive oil and ancho chili powder, then toss those babies in with the haricots verts.
Or just toss the warm haricots verts with some form of dressing. Suggested dressings: chopped toasted walnuts and a drizzle of walnut oil; a little butter and a little soy sauce; olive oil, lemon zest, and pecorino; or the very traditional Georgian combination of minced garlic, chopped cilantro, olive oil, and toasted walnuts.