Toss potatoes in 1 Tbsp olive oil, salt & pepper to taste.
Grill covered, over medium heat until brown and soft, about 5 to 7 minutes per side.
Toss beef with 2 Tbsp. olive oil and season with salt & pepper. Thread beef into 4 separate skewers. Grill over medium-high heat, to desired doneness (about 4 mins per side for medium).
Transfer skewers to a plate and rest for 5 minutes. Brush with chimichurri while the kebabs are resting (Cover with foil to keep them warm).
Vinaigrette: Whisk ingredients (except the oil). Continue to whisk the ingredients while adding the oil slowly. Season with salt & pepper.
Make a simple salad with lettuce, tomatoes, and cucumbers. Toss with some vinaigrette.
Serve skewers warm with potatoes, chimichurri sauce & salad.