Palak paneer is one of the most universally loved vegetarian dishes across the subcontinent, and one that is consistently ruined by overcooking the spinach into a grey-brown mush. The secret to vivid green palak paneer is speed: blanch the spinach briefly, shock it in ice water immediately to stop the cooking, and blend it quickly. The entire purée step should take under 5 minutes.
Paneer is the other variable. Shop-bought paneer is often dry and rubbery. The solution is to either buy fresh paneer from a South Asian grocer (where turnover is high) or make it yourself (just two ingredients: whole milk and lemon juice). Pan-frying the paneer in ghee until golden before adding it to the curry creates a slight crust that holds up in the sauce.