Housemade Steak Sauce
In a large saucepan, sweat onion and garlic. Add sugar, molasses and corn syrup and reduce until mixture is syrupy. Add concentrate, vinegars and raisins and return to a simmer; reduce. When mixture is reduced, add ketjap manis and tomato purée. Bring to a simmer and then add all remaining ingredients; continue simmering for 30 minutes. Purée in a blender, adjusting consistency with chicken broth. Keep warm until ready to serve.
Preheat the oven to 300°F.
Peel potatoes and square them by slicing off rounded edges. Using a mandoline, cut each potato lengthwise into 1/8-inch thick slices. Shingle in a single layer half way up the sides of a sheet pan. Season with salt, pepper, garlic confit and thyme sprigs.
Cook, covered for 45 minutes. Uncover and remove thyme sprigs. Add reduced cream to cover. Cook gratin another 10 minutes, until cream is absorbed. Add more cream and continue cooking 10 more minutes. Remove from oven. Season with kosher salt and white pepper; set aside to cool.
Heat oil in rondeau or heavy skillet and sweat onions until translucent. Fold in Gorgonzola and stir until melted. Remove from heat. Cool and then strain off excess liquid through a large-holed colander. Spread strained mixture over potato gratin.
Preheat oven to 350°F.
Cut potato gratin into single serving pieces. Sprinkle each serving with seasoned Japanese breadcrumbs. Heat in oven at 350°F for about 10 minutes or until potatoes are heated and breadcrumbs are golden brown.
While potatoes are heating, prepare flat irons. Heat a little oil in a large sautépan over medium-high heat. Add meat and cook about 4 minutes per side or until medium-rare (175°F). Add butter and rosemary; baste meat until butter foams. Remove from pan and place on rack to rest.
To serve, place 1 serving of potato gratin on each plate. Slice flat irons and arrange slices on top. Spoon steak sauce around potato gratin and garnish with rosemary sprigs.
Chef Note: Ketjap manis or kelap mais is an intensely brown, syrupy-thick Indonesian sauce found in Asian markets.
Housemade Steak Sauce
- 1 small Spanish onion, diced
- 5 cloves garlic, minced
- 1/4 Cup granulated sugar
- 1/4 Cup molasses
- 1/4 Cup corn syrup
- 2 Tablespoons orange juice concentrate
- 1/2 Cup plus 2 tablespoons malt vinegar
- 1/2 Cup red wine vinegar
- 1 Cup California raisins
- 1/2 Cup ketjap manis
- 1/4 Cup tomato purée
- 1/4 Cup lemon juice
- 1/2 Tablespoon dried basil
- 1/4 Cup grapefruit juice
- 1/4 Cup Worcestershire sauce
- 2 Cups chicken broth
- 2 large Idaho potatoes
- 2/3 Cup minced roasted garlic cloves
- 4 sprigs fresh thyme
- 1 Cup reduced heavy cream
- Kosher salt and freshly ground white pepper
- 3 Tablespoons blended oil
- 1 large white onions, cut in matchstick-size pieces (julienne)
- 2/3 Pound Gorgonzola cheese, broken into small chunks
- 4 flat irons of beef (4 ounces each), trimmed and seasoned with salt and pepper
- 1/4 Cup (2 ounces) unsalted butter
- 4 small sprigs fresh rosemary
- Japanese breadcrumbs
- Oil, as needed