Undersea electricity transmission cable between Africa & EU
Many Europen nations have a surplus of electricity generating capacity. A cable laid across the Straits of Gibralter would enable electricity to be transmitted & sold to African nations which were connected up to a common electricity grid. The funding for such a cable (and the transmission grid) could come from a European sponsored 'Marshall Aid' type plan for Africa. This would further economic development in Africa and ease immigration pressures on Europe simultaneously. A classic win-win situation for all!
Reward: Prosperity in Africa, stability in Europe.