Preheat the oven to 180 degrees C. Grease two 20cm round cake tins, or 23cm pie dishes.
In a large bowl, use an electric mixer to beat butter and sugar until light and fluffy. Add eggs, reserving just enough to brush over the tops, about 1 tablespoon. Stir in the almond essence. Combine the flour and baking powder; stir into the batter by hand using a sturdy spoon. The dough will be stiff.
Press evenly into the two prepared tins. Press almond halves into the top where each slice would be. Brush the tops with a thin layer of the reserved egg.
Bake in the preheated oven for about 30 minutes, or until the top is golden brown. Cut into wedges to serve.