Pub street in Siem Reap is near the Old Market is a great spot to head to find lots of great restaurant options in the one place like Cambodian BBQ, Red Piano, Amok, Khmer Kitchen Restaurant, Chamkar, and Blue Pumpkin for icecream.
Red Piano
Khmer Kitchen Restaurant
Fireworks for the Water Festival Blue pumpkin coconut, durian and black sesame and ginger (yum) ice-cream
Sister Srey Cafe is a bit further away, but also worth checking out.