I found the restaurants in Luang Prabang to be really outstanding. My favorites were L’Elephant and Paste at the Apsara hotel. The Belmond La Residence Phou Vao had a really good restaurant with stunning views.
I recently read about La Belle Rive for dining along the Mekong River, Manda de Laos for fine dining in a beautiful setting on a lilly pond, Chez Matt for wine and cocktails, Le Banneton Café for French-style baguettes, pastries, and coffee and the casual Le Bistro Ban Vat Sene. It is ideal for breakfast, lunch, a tea break, dinner or just for cocktails.