Put the olive oil in a large, non-stick frying pan with a tight-fitting lid. Add the streaky bacon. Cook for 8-10 mins until the fat has been released and the bacon is crisp, then transfer to a plate using a slotted spoon.
Put the popcorn kernels in the pan and coat in the fatty bacon residue. Cover with a lid and cook until the corn is nearly all popped – about 4 mins). Melt the unsalted butter in the microwave for 10 secs. Once the popcorn has puffed up, coat in the butter and scatter over the bacon and a little salt.