As a chocolate lover myself I researched the nutritional benefits of chocolate.
Milk chocolate is a food craved by many of us because it contains that magic 50:50 ratio of fat: sugar and the only other unprocessed source that has an equal amount fat and sugar is breast milk, your first ever food! 
Chocolate with a high cocoa content, i.e. dark chocolate, is a well-known staple of the Mediterranean diet. 
 Moseley, M.M., The Clever Guts Diet, 1st edn. London: Short Books; 2017.
What are the nutrients of cocoa?
Cocoa (Cacao), the main ingredient of chocolate contains many trace minerals including potassium, phosphorus, copper, zinc, and magnesium all of which help us with the processes in the body, such as brain function, digestion, energy production.
If you are craving chocolate, it might be worth reviewing your magnesium levels since that is a key mineral to produce energy.
Chocolate can vary a lot in richness of nutrients. Cacao before roasting to cocoa has the most, closely followed 90% dark chocolate, then 70+% dark chocolate, then milk chocolate and lastly white chocolate (contains only milk and sugar so is not nutrient rich).
The plant-based nutrients (phytonutrients) in cocoa include caffeine (nervous system stimulant), methylxanthine and theobromine, both diuretic and smooth muscle relaxants. Cocoa also contains flavonoids (antioxidants).
Free radicals are highly reactive molecules in the body that have the capacity to affect body cells and trigger further inflammation. Antioxidants support the body to limit free radicals
Cocoa is broken down in the large intestine to produce nitric oxide, a chemical in the body which can help to expand arteries in the body – good for the cardiovascular system1.
Studies are emerging for the benefit of cocoa and weight management, which assumes quality low sugar chocolate or pure cacao (you can buy as a powder or nibs in health food shops). A 3-week study in rats for example noticed some reduction in weight which might be due to a reduction in fat absorption.
 Mohd Mokhtar, et al., The effect of Malaysian cocoa extract on glucose levels and lipid profiles in diabetic rats. Journal of ethnopharmacology. 2005, 98. 55-60.