Prepare the potatoes: Start by peeling, slicing, washing, and drying your russet potatoes.
Sear the potatoes: Sear them in some hot oil until they're lightly golden brown.
Add garlic, onions, and butter: Flip the potatoes over, add garlic, onions, and a whole bunch of butter.
Simmer: Turn the heat down to medium-low and let them simmer in the hot foaming butter. Make sure to flip them over every 15 minutes so they cook and brown evenly. This should take about an hour and 15 minutes total.
Save the butter: Save the leftover butter for general cooking.