A method is provided to prepare a food product with a favorable nutritional composition that is easy to prepare and can suitably be used in for example fast food outlets. Cooked patties are stored in packaging at a temperature below 10°C. The cooked patties have a moisture content of 70-90 wt% and a fat content of 1-15 wt%. They comprise gelled protein and vegetable particles, and they comprise protein and carbohydrate in a weight ratio of at least 1.5:1. In the method a patty is separated from the packaging and taken from the storage and is subsequently subjected to a dry heat treatment to raise the temperature of the interior of the patty to above 40°C. Also provided is a pack containing frozen semi-finished food product suitable for use in the present method. The pack comprises cooked patties with a moisture content of 70-90 wt% and a fat content of 1-15 wt%, which comprise gelled protein and vegetable particles, which comprise protein and carbohydrate in a weight ratio of at least 1.5:1 and which have an interior temperature of less than -4°C.