Step 1

Preheat oven to 180C and butter a 25cm diameter ovenproof dish. Heat oil in a frying pan over medium-high heat, add bacon and fry until crisp (2-3 minutes), then add garlic and stir until fragrant. Set aside.

Step 2

Place cream in a bowl. Thinly slice potatoes on a mandolin straight into the cream and season generously. Layer potatoes in prepared dish, scattering bacon, onion and a little parmesan between layers and seasoning well as you go. Pour cream over the top to cover (you may not need it all) and dot with cubes of butter. Place on a baking tray lined with baking paper and bake until golden brown and bubbling (50 minutes to 1 hour).

Step 3

Combine breadcrumbs in a bowl with melted butter and paprika, season to taste and scatter over gratin, then scatter with a little extra parmesan. Continue to bake until crumbs are golden (6-8 minutes), stand for 10 minutes, then serve with the roast beef.