Method
Step 1
Preparation: Preheat the oven to 200°C. Prepare all ingredients as indicated above.
Step 2
Sweet potato chips: Cut off the ends, then cut into 1cm slices lengthways and cut those slices into 1cm chips. Place on a tin foil lined baking tray. Drizzle with olive oil, season with salt and pepper, mix and then spread in a single layer. Roast for 25 minutes, until golden and cooked.
Step 3
Caramelised onion: Place a pan on low-medium heat with a generous knob of butter. When the butter has melted, add the onion with a pinch of salt. Cook for 20 minutes, stirring every now and then, until soft and slightly sweet.
Step 4
Mayo sauce: Mix together the mayonnaise, garlic and wholegrain mustard. Set aside.
Step 5
Patty: Mix together the beef mince and fresh rosemary (use half the quantity of rosemary), season generously with salt and pepper and shape into a patty. Add a drizzle of olive oil to a pan on medium-high heat. When hot, add the patty (it should sizzle when it hits the pan) and cook for 4-6 minutes per side until cooked to your preference.
Step 6
Serve the patty topped with the mayo sauce and caramelised onion. Mix together the tomatoes and baby spinach and serve on the side with the sweet potato chips.