Place steak on a clean, flat surface. Score meat in diagonal lines about 2-inches apart with a knife.
Pound steak with the spiked side of meat mallet to tenderize a bit. Cover with plastic wrap to keep area clean, then finish off with the flat side of mallet until about ⅛-inch thick. Sprinkle both sides with salt and pepper. Set aside.
In a medium bowl stir together dip, spinach (if using frozen spinach cook first then press into a fine mesh strainer to drain liquid), garlic and green onions. Spread mixture over steak, leaving a bit space at edges.
Roll filled flank steak from one edge and use multiple toothpicks to secure edge. Cut into roughly 1-½ inch slices with a very sharp knife.
Place pinwheels on a foil-lined baking sheet at least 2-inches apart. Set oven to high broil and place pan 4-5 inches from heat. Broil each side 3-4 minutes, until medium or about 145° F. Check often and don’t overcook the meat. Let rest a few minutes then serve.
Use high-quality flank steak, preferably organic or grass fed
Scoring meat with a knife helps with flattening.
Covering steak with plastic wrap while pounding prevents splashing
Cooking and draining frozen spinach prevents water from drawing out while cooking pinwheels
Each pinwheel should have a toothpick in it to seal the edge