Preheat the oven to 425°F (220°C). Grease the ring and base of a 10-inch springform pan.
Whisk the eggs and sugar together until thick and creamy. Then stir in oil and orange juice until combined thoroughly.
Quickly mix in the flour and baking powder. Turn the oven down to 400°F (200°C, top heat only, if available).
Spread about 4 tablespoons of cake batter on the bottom of the baking pan to cover completely in a thin layer. Bake in the lower part of the oven for approx 5-8 minutes, or until light brown. (Note: Keep an eye on it! The first thin layer can burn quickly.)
Take the cake out of the oven and spoon another 4 tablespoons of batter into the pan, spreading it in an even layer over the first layer. Bake again for 5-8 minutes.
Spread 3 tablespoons of apricot jam on top of the second layer.
Keep baking layers one on top of the other in the same order. Every third layer should be apricot jam. The last layer should be batter.
After baking the last layer, let the cake cool completely on a wire rack. Remove from the pan.
Melt the dark chocolate in the microwave or a double boiler. Spread another layer of apricot jam on the cake, then pour the chocolate on top and spread to coat.
Melt the white chocolate and drizzle in decorative patterns over the dark chocolate, if desired. Or decorate the cake as shown with leaf-shaped chocolates. These can be made in a candy mold, using melted dark or milk chocolate.