680 g (1.5 lb) chuck roast, cut into 1 cm (½ inch) chunks, well chilled
1 large egg, beaten
½ cup Italian-seasoned breadcrumbs
1 tbsp whole grain mustard, plus more for serving
1 tbsp Worcestershire sauce
2 tsp steak seasoning
30 mL (2 tbsp) olive oil, divided
1 large yellow onion, thinly sliced into half moons
1 cup cremini mushrooms, thinly sliced
1 tbsp butter
2 tsp canola oil
200 g (2 cups) blue cheese, crumbled
Salt and freshly ground black pepper, to taste
4 burger buns, for serving
Directions
Fit a stand mixer with a meat grinder attachment. Grind the chilled chuck on a coarse setting. Keep all equipment and meat well chilled for best texture.
In a large bowl, combine the ground beef, egg, breadcrumbs, mustard, Worcestershire, and steak seasoning. Season lightly with salt and pepper. Mix just until combined. Form into 4 equal patties and refrigerate.
Heat 15 mL (1 tbsp) olive oil in a medium frying pan over medium-high heat. Add the onion and mushrooms. Cook until lightly browned, then reduce heat to low. Cook, stirring occasionally, for 25–30 minutes until deeply caramelized and jammy. Season to taste.
Heat butter and canola oil in a large cast iron skillet over medium-high heat. Add the burgers and cook for 5–6 minutes per side, or until a digital thermometer reads 71°C (160°F).
Top each burger with the onion-mushroom mixture and blue cheese. Cover the pan and let sit off heat for 2–3 minutes until the cheese melts slightly.
