Preheat the oven to 180°C and line a baking tray with parchment paper with vegetable oil spread underneath to prevent slipping

Using a stand mixer with a whisk attachment fitted, beat the eggs, sugar and vanilla bean paste for the roulade sponge together until pale, thick and a ribbon consistency

Add in the melted butter and whisk until combined. In a separate bowl sift together the Doves Farm oat flour, xanthan gum and baking powder

Add the dry ingredients to the wet ingredients and whisk until no clumps remain. Transfer the mix to the lined baking tray, smooth it out using a palette knife and clean the edges with your finger. Bake for 10 minutes in the oven

Once you remove the sponge from the oven, wrap it tightly in a large sheet of aluminium foil – avoiding touching the surface of the sponge to reduce the chance of sticking. Allow it to cool to room temperature

In a stand mixer fitted with the whisk attachment, beat the soft, unsalted butter until smooth, then add in the remaining hazelnut buttercream ingredients. Add a couple of tablespoons of milk and mix until the buttercream is soft enough to spread but firm enough that it won’t collapse as you roll up the sponge

Dust a sheet of parchment that's bigger than the roulade all over with icing sugar. Once the roulade is at room temperature, flip the sponge onto the sugar-coated parchment. Remove the layer of parchment paper stuck to the cake

Spread a 1 cm layer of the buttercream over the sponge. Rotate the sponge so the short edge is closest to you then, using icing sugar-dusted parchment paper, roll up the sponge

Tuck the parchment paper under itself to support the roll and trim off the excess. Place the roulade in the fridge to chill for 2 hours

Prepare the toasted hazelnut and cinnamon crumble by pulsing together all the ingredients in a food processor until they form a crumb

To make the ganache glaze, place the dark chocolate in a heat-proof bowl

Warm the double cream over a medium heat until it just begins to simmer

Pour the hot cream over the chocolate and allow to sit for 2–3 minutes, then stir together until smooth and glossy

Cool the ganache in the fridge, stirring occasionally, until the glaze is viscous enough to coat the cake

Trim both the edges off the roulade to make it neater, then place the chilled roulade onto a wire rack over a rimmed baking sheet. Pour the ganache glaze over the chilled roll, making sure to fully cover the cake

Sprinkle over the hazelnut crumb, then place in the fridge to chill for 20 minutes

Use a hot knife to slice and serve