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Compound Butter Prawns, Wagyu Rump Cap & Grilled Cos

Lachlan Whittle

Servings

4-6

Prep Time

45 minutes

Cook Time

45 minutes

Cuisine

Australian

Category

Dinner

Learn how to cook compound butter prawns, wagyu rump cap, and grilled cos lettuce on the Big Green Egg. This Australian BBQ recipe layers five-chilli compound butter, overnight dry-brined wagyu picanha, and cherry-charred cos for a live-fire feast built entirely on the Egg. Packed with bold flavour and perfect for entertaining, this is high-heat Big Green Egg grilling at its best — smoky, fast, and completely unapologetic.

Compound Butter Prawns, Wagyu Rump Cap & Grilled Cos

Ingredients

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    • 400g (14 oz) Unsalted butter, softened to room temperature

    • 1 Dried ancho chili

    • 1 Dried pasilla chili

    • 1 Dried guajillo chili

    • 1 Dried morita chili

    • 1 Dried de arbol chili

    • 1 tbsp Achiote paste

    • 2 tbsp Garlic chives, finely chopped

    • 3 cloves Garlic, finely minced

    • 1 Chipotle chili in adobo sauce (from can)

    • 1 Lime — zest and juice

    • 1 tsp Ground cumin

    • 1 tbsp Salt

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    • U6 prawns, butterflied through the back and cleaned

    • Cinco Chilli Rub

    • Neutral oil

    • Smoked Pineapple Habanero Hot Sauce

    • Fresh coriander, finely chopped, and lime wedges

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    • 1 whole Wagyu rump cap (picanha), cut into 40mm steaks

    • Flaked salt (for overnight dry-brine and final seasoning)

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    • Cos (romaine) lettuce heads, outer leaves removed, halved lengthways

    • 2 tbsp Garlic-infused olive oil (or 1 clove garlic minced into 2 tbsp olive oil)

    Directions

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      1. De-stem and de-seed all dried chilies — ancho, pasilla, guajillo, morita and de arbol — then cut into chunks using scissors.

      2. Toast the chili pieces in a dry, hot frying pan for 30–45 seconds, moving them constantly. You want fragrant and toasted, not burnt — burnt chilli turns bitter.

      3. Remove from heat and allow to cool completely. Once cool, grind in a spice grinder until broken down but still slightly chunky.

      4. In the same hot pan, toast the achiote paste briefly to fry it out and deepen its flavor. Add to the spice grinder with the chili and pulse to combine.

      5. Transfer the chili-achiote blend to a mixing bowl with the softened butter. Add the minced garlic and chopped garlic chives and mix well.

      6. Add the chipotle chili in adobo, lime zest, lime juice, ground cumin and salt. Mix thoroughly until evenly incorporated.

      7. Lay a square of baking paper flat. Spoon half the butter in a log across the center, roll into a tight cylinder, wrap in cling film and twist the ends to seal. Repeat with remaining butter.

      8. Freeze until firm. When ready to cook, remove one stick and slice into 5mm discs.

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      1. Cut the whole rump cap into 40mm steaks. Season generously with flaked salt on all sides, then place uncovered on a rack in the fridge overnight.

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      1. Set up for direct grilling — no convEGGtor. Bring the Egg up to high heat: 230–260°C / 450–500°F.

      2. Allow the grill grate to heat fully before any food goes on.

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      1. Remove steaks from the fridge 30 minutes before cooking. Season all sides with a little more flaked salt just before they go on.

      2. Place steaks fat-cap side down on the hot grill. Render as much fat as possible — allow 3–5 minutes depending on thickness.

      3. Once the fat cap is well rendered and golden, flip the steaks. Rotate every 30–45 seconds until the internal temperature reads 45–46°C (113–115°F) — rare to medium-rare, ideal for wagyu.

      4. Remove from the Egg and rest uncovered for a minimum of 10 minutes before slicing.

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      1. Open the butterflied prawns and press firmly against a chopping board to flatten them.

      2. Flip shell-side up. Drizzle with neutral oil and season with Cinco Chilli Rub.

      3. Slice compound butter into 5mm discs and place directly onto the body and head of each prawn.

      4. Place prawns on the hot grill over direct heat. Cook for 3–4 minutes until the flesh turns opaque and the edges curl slightly.

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      1. Remove outer leaves from each cos head and halve lengthways. Brush garlic-infused olive oil generously over all sides.

      2. Place flat-side down on a cooler part of the grill first, then move to the hotter zone to finish.

      3. Remove when charred but still holding its shape — outer leaves caramelized, interior still crisp.

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      1. Rest the wagyu steaks for at least 10 minutes, then slice against the grain and arrange on a large board or platter.

      2. Transfer prawns directly from the grill to the plate. Finish with a squeeze of fresh lime and finely chopped coriander.

      3. Add the charred cos halves alongside.

      4. Drizzle hot sauce generously over the prawns.

      5. Serve everything family-style in the center of the table.

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