Before starting, preheat the oven to 450°F. Wash and dry all produce. Cut cauliflower into bite-sized pieces. Toss cauliflower with 1 tbsp oil (dbl for 4 ppl) on a baking sheet. Season with salt and pepper. Roast in the middle of the oven, stirring halfway through cooking, until golden-brown, 17-18 min.

While cauliflower roasts, peel, then mince or grate the garlic. Heat a large non-stick pan over medium heat. When hot, add panko to the dry pan. Cook, stirring often, until toasted, 2-3 min. Remove the pan from heat, then transfer toasted panko to a plate. Set aside. Carefully wipe the pan clean.

Heat the same pan over medium-high heat. When hot, add 1 tbsp oil (dbl for 4 ppl), then onions. Cook, stirring occasionally until slightly softened, 3-4 min. Add beef, broth concentrate and half the garlic, then season with salt. Cook, stirring occasionally, until shredded beef heats through, 3-4 min. (NOTE: if the beef mixture is dry add, 2 tbsp water (dbl for 4 ppl) and stir to coat.)

While the beef cooks, stir together the horseradish, whole grain mustard and half the mayo in a small bowl. Season with salt and pepper.

Halve rolls and arrange them, cut-side up, on another baking sheet. Toast rolls in the top of the oven, until golden, 2-3 min. (TIP: Keep an eye on the buns so they don't burn!)

Stir together remaining mayo and remaining garlic in a large bowl. Toss roasted cauliflower with the garlic-mayo. Sprinkle with toasted panko, then stir to coat. Spread horseradish aioli over bottom rolls, then top with spring mix and shredded beef mixture. Divide beef sammies and cauliflower frites between plates.