Via: Evan Sung
Preheat the oven to 180°C/fan 160°C/gas mark 4. Arrange the hazelnuts on a rimmed baking sheet and toast for 12-15 minutes until golden brown, shaking the pan halfway through roasting. Leave the hazlenuts to cool, then transfer to a food processor and grind for 1-3 minutes until they become a smooth paste, scraping down the bowl as needed.
Add the sugar, honey, icing sugar, oil and 1 tsp salt to the nut butter, and blend until combined. Add the melted chocolate and process until combined, then scrape the mixture into an airtight container and leave out at room temperature to thicken for 3 hours, or overnight.
Spread the bread slices with the butter, and sprinkle with 1 tsp flaky salt. Toast under the grill for 1 minute. Remove from the grill,and swipe some chocolate-hazelnut spread over each slice. Top with a handful of marshmallows. Position an oven rack in the top third of the oven, then return the baking sheet to the grill. Grill the toast for 15-30 seconds until the marshmallows are golden brown. Keep a close eye to make sure they don't burn. Let the toast cool for 1-2 minutes before serving.
Toast by Raquel Pelzel (Phaidon, £14.95)