Cook onion in large oiled pan, stirring, until soft.
Add spices; cook, stirring, about 1 minute or until fragrant.
Add potato, peas, lentils and stock.
Bring to boil; simmer, covered, about 1 hour or until peas are tender, [can be prepared ahead to this point; refrigerate overnight or freeze] Blend or process lentil mixture, in batches, until smooth; return to same pan.
Stirin coconut milk and juice; reheat without boiling.