Argentina is known for fine beef, potatoes, and flavorful seasonings. Its most famous sauce is chimichurri, which is used here to dress the potato salad and as a dipping sauce for the spice-rubbed grilled steak.
For the Chimichurri, place all ingredients in food processor; cover. Process until parsley is coarsely chopped
Cook potatoes in lightly salted boiling water 8 to 10 minutes or until tender. Drain well. Refrigerate 1 hour. Just before serving, add celery and red bell pepper. Toss with 1/2 cup of chimichurri sauce
Rub flank steak with oil. Mix ancho chile pepper, pepper, thyme and salt in small bowl. Sprinkle the spice mixture evenly over both sides of the steak. Refrigerate 1 hour
Grill over medium-high heat 6 minutes per side or to desired doneness. Serve with remaining chimichurri sauce and potato salad