Leave the ice creams out at room temperature for a few mins to soften slightly. Brush a 1.2-litre loaf tin with the vegetable oil and line with cling film. Put 250g dark chocolate and the coconut oil in a small heatproof bowl over a pan of just simmering water. Stir to melt, then set aside to cool.

Spoon half the coffee ice cream into the base of the tin and level the surface. Working quickly, spread over a quarter of the chocolate sauce, then half the vanilla ice cream and another quarter of chocolate sauce. Repeat with the remaining chocolate sauce and ice creams, finishing with a layer of chocolate sauce. Cover loosely with cling film and freeze for at least 2 hrs, or ideally overnight.

Melt the remaining 50g chocolate in a heatproof bowl over a pan of simmering water. Lift the terrine out of the tin and turn out onto a plate. Drizzle with the melted chocolate and top with the crushed honeycomb or Maltesers. Cut into thick slices to serve.