I got curious about Bulletproof coffee and decided I needed to cut down on my caffeine intake. Anyways, I spoon about 10 heaped tablespoons of Expresso grade grounds into (its actually a large ceramic percolator with the percolation bits removed - the largest container that’ll fit in my fridge) and cover that with cold water. The lid wont fit due to the height so I cover it with ceram wrap to eliminate the possibility of any unwanted fridge odours. 24 hours later I pour that off (down to the grounds) through a strainer and keep it ready in the fridge to use. (Keep the grains out or it will taint the batch). This makes a very robust brew and I read about diluting the result but i like it as it is. When I want a mug I just nuke the cold stuff and instead of milk I put about a 1/4 inch thick postage stamp sized dob of butter (they say unsalted but regular is probably just as good - the salt might even enhance the taste) and a big dob of Coconut cream (not milk) - for the medium chain fatty acids. You don’t have to go all purist about buying MFC’s or “grass fed” butter grown on the lee side of a south facing hill. It tastes great and is filling and I only need about 2 mugs a day. One negative is that when I revert to my (quite strong) instant I now use 2 spoons of coffee as i am used to a stronger brew. Reading this it might sound like a heap of work but it is actually dead simple. Taste and try.