Trim the hazelnut sponge and slice lengthwise into 3 strips, 3 by 16 in/8 by 41 cm each.
Combine the buttercream with the praline paste and mix until smooth.
Moisten one of the sponge strips with one-third of the syrup, and spread 4 oz/110 g of the buttercream mixture over it. Place a second strip on top of the buttercream, moisten with another one-th