It's true, according to Einstein's special theory of relativity there is enough energy in a mars bar to blow up Europe.
Here's how it works: E = mc2
m = mass of the Mars bar = 56g
c= 186,000 x 186,000 = 34,596,000,000
E = 56 x 34,596,000,000
= 1,937,376,000,000 joules
Don't confuse these joules (potential energy) with the Kilo joules in the nutritional information.
Now, 1 kilo joule will move one kilogram 1 metre. So there is enough energy in a Mars bar to move 1 kilogram by 1,937,376,000 metres easily enough energy to blow up Europe.