1.Place apple and the water in a large saucepan; cover surface with a round of baking paper, then a small plate to weight it down. Bring to the boil over high heat. Reduce heat; simmer, for 20 minutes or until apple is soft. Drain. Cool. Blend or process apple, in batches, until smooth. Transfer mixture to a large bowl; stir in brown sugar and spices.
2.Preheat oven to 180°C. Grease and line two oven trays with baking paper.
3.Beat butter, caster sugar and extract in a small bowl with an electric mixer until pale and fluffy. Beat in eggs, one at a time, until just combined. Transfer mixture to a large bowl. Sift flours, soda and salt into another large bowl. Stir flour mixture into creamed mixture alternately with buttermilk, in three batches, until combined (mixture will be stiff; you may need to finish combining with your hands). Knead dough on a floured surface until smooth and combined.
4.Divide dough into eight equal portions. Roll one portion of dough between sheets of baking paper into a 23cm round. Using a 22cm plate or cake pan as a guide, cut round from dough. Transfer to one tray. Repeat with another portion of dough and second tray. Bake rounds for 12 minutes, swapping trays from top to bottom halfway through cooking time or until golden. Leave rounds on trays for 5 minutes before transferring to wire racks to cool. Repeat process with remaining dough portions, baking in batches, to make eight rounds in total.
5.Place one cake round on a platter or cake stand; spread with a slightly rounded ½ cup of apple filling. Repeat layering with remaining cake rounds and apple filling, finishing with a cake round. Cover cake with plastic wrap; refrigerate overnight.
6.Make toffee apples (see steps below).
7.Just before serving, dust cake with icing sugar; top with toffee apples, drizzle with reserved toffee.
8.Line an oven tray with baking paper. Push a bamboo skewer halfway into the core of each apple through the stem end. Stir sugar, glucose and half the water in a medium saucepan over low heat until sugar dissolves. Bring to the boil over high heat; boil for 7 minutes or until golden brown.
9.Remove from heat. Working quickly, tilt pan slightly to one side and carefully dip an apple in toffee, twisting slowly to coat the apple completely.
10.Remove apple slowly, twirling around a few times over pan to drain off excess; place on tray. Repeat with remaining apples and toffee.
11.Leave apples at room temperature until set; remove skewers. Return pan to heat; stir in the remaining water until combined. Reserve toffee.
You will need to start this recipe the day before. You need five bamboo skewers for the toffee apples; push a skewer into the core of each baby apple before dipping into the toffee. You can make this cake up to 2 days ahead; store, in an airtight container at room temperature. Decorate cake with apples before serving.