Begin by heating a frying pan over medium-high heat. Add vegetable oil, then sear the topside beef roast for about 3–4 minutes on each side. Toss in the halved garlic bulb and onions, browning them for an additional 2 minutes. Transfer to the slow cooker.

In the same frying pan, pour in beef stock and bring to a gentle boil, scraping the browned bits. Whisk in brown miso paste and tomato purée until combined. Pour over the beef in the slow cooker.

Add black peppercorns, bay leaves, and rosemary into the slow cooker. Secure the lid and cook on high for 1.5 to 1.75 hours, or low for 2 hours and 20 minutes, until beef reaches 60°C (140°F).

Once cooked, carefully remove the lid and let the beef rest in the cooker for 30–40 minutes.

Strain the cooking liquor into a saucepan, pressing on the onions. Discard solids and skim off fat. Mix cornflour with some strained liquid to create a slurry and stir back into the saucepan.

Heat the gravy mixture over medium heat, stirring constantly for about 10–15 minutes until thickened. Serve with sides like creamy mashed potatoes or roasted vegetables.