In a shallow bowl, combine 2 tbs olive oil, 1 tsp smoked paprika, 1/2 tsp garlic powder, 1 tsp kosher salt and 1/2 tsp black pepper. Coat both sides of the chicken breasts in the mixture and let rest 10 minutes at room temperature (or refrigerate up to 1 hour).

Heat a grill pan or outdoor grill to medium-high (about 425°F/220°C). Oil the grates or pan lightly. Grill the chicken 4-6 minutes per side, or until an instant-read thermometer inserted in the thickest part reads 165°F (74°C). Let rest 5 minutes, then slice to fit the buns.

While chicken rests, split brioche buns and spread 1/2 tbs softened butter on cut sides. Toast buns on the grill or in a skillet until golden, about 1-2 minutes. Keep warm.

Guinness BBQ Sauce

In a small saucepan over medium heat, add 1/2 cup Guinness and bring to a simmer. Reduce slightly for 2-3 minutes.

Add 1/2 cup ketchup, 2 tbs brown sugar, 1 tbs apple cider vinegar, 1 tsp Worcestershire sauce, 1 tsp Dijon, 1 tsp soy sauce, 1/2 tsp smoked paprika and 1/4 tsp black pepper. Whisk to combine.

Bring sauce to a gentle simmer and cook, stirring occasionally, until slightly thickened, about 6-8 minutes. Taste and adjust seasoning (more sugar for sweetness or more vinegar for tang). Keep warm. Reserve 3 tbs for brushing the chicken and serve remaining on the side.

Roasted Garlic Mayo

Preheat oven to 400°F (200°C). Slice the top 1/4 inch off the head of garlic to expose cloves. Drizzle 1 tsp olive oil over the exposed cloves, wrap the head in foil and roast 30-35 minutes until cloves are soft and caramelized.

Let garlic cool slightly, then squeeze roasted cloves into a small bowl. Mash with a fork and stir into 1/2 cup mayonnaise with 1 tsp lemon juice, 1/4 tsp salt and 1/8 tsp black pepper. Refrigerate until ready to assemble.

Pickled Onion & Toppings

Place 1/2 cup thinly sliced red onion in a small jar or bowl. In a microwave-safe measuring cup or small saucepan, combine 1/4 cup white vinegar, 1/4 cup water, 1 tsp sugar and 1/2 tsp salt and heat until sugar and salt dissolve (about 20-30 seconds in microwave or 1-2 minutes on stove). Pour pickling liquid over onions and let sit at least 15 minutes (or up to several hours refrigerated) to develop flavor.

Wash and dry iceberg leaves and slice tomato into 2-4 slices. Keep ready for assembly.

House Fries

Preheat oven to 425°F (220°C) if roasting. Scrub potatoes and cut into 1/4- to 1/2-inch fries. Place fries in a bowl of cold water and soak 15 minutes to remove excess starch, then drain and pat very dry with towels.

Toss dried fries with 3 tbs vegetable oil, 1/2 tsp garlic powder, 1/2 tsp paprika, 1 tsp kosher salt and 1/4 tsp black pepper until evenly coated.

Spread fries in a single layer on a rimmed baking sheet lined with parchment. Roast 25-30 minutes, flipping once halfway, until golden and crisp. Alternatively, deep-fry at 350°F (175°C) until golden, 3-4 minutes, then drain on paper towels and season immediately.

Assembly

Brush the sliced, rested chicken with about 1-1.5 tbs of the warm Guinness BBQ sauce on both sides.

Spread 1-2 tbs roasted garlic mayo on the bottom bun. Place a lettuce leaf and a slice or two of tomato on the mayo. Add the BBQ-glazed chicken on top.

Top the chicken with a generous handful of pickled onions. Spoon additional Guinness BBQ sauce on the top bun if desired, then close sandwich.

Serve each sandwich with a portion of house fries and remaining BBQ sauce on the side for dipping.