Well just to update, I tried this last night. I didn’t get to read @netgrrl‘s response before I made my brew, so I ended up using ½ cup of ground coffee in 1.5 quarts of water. I left it over night in a plastic container in the fridge. I filtered it this morning using a plastic mesh filter (don’t have any paper filters). The result was delicious, but a bit cloudy and nowhere near strong enough for me. You could drink it neat without diluting, so would be great for iced coffee but personally I like it hot. Next time I would use more coffee and leave it for longer to make it more like a concentrate, and I’m going to buy some paper filters to reduce the cloudiness.
Otherwise I really like it! A smooth, yet rich and almost chocolaty flavour. You definitely don’t need to spend the money on a toddy (although I would love to compare my home made brew with a toddy brew, just out of interest). As for reduced caffeine content, I’m not so sure – my heart’s still pounding like a jack hammer!