Heat oil in a large, deep non-stick frying pan over a medium-high heat. Add chicken and onion. Cook, stirring occasionally, for 6-8 minutes, until lightly browned.
Add tikka paste. Cook, stirring, for 1 minute or until fragrant.
Add rice and stir until well coated. Stir in stock and 2½ cups water. Bring to the boil. Reduce heat and cover with lid. Simmer, covered, for about 20 minutes, until stock is almost absorbed.
Stir in broccolini. Cook, covered, for a further 5-10 minutes, until liquid is absorbed and rice is tender.
Stir in spinach, coriander and half the yoghurt. Remove from heat. Stand, covered, for 1-2 minutes, until spinach is just wilted.
Sprinkle over cashews. Serve with remaining yoghurt and lemon wedges.