Heat up spices in a large saucepan over medium-low heat slowly until spices begin to “crackle” a bit.
Turn off the heat and add the cubed butter to the pan with the spices. Simmer butter on low until medium-dark (almond-brown) in color. Remove from the heat and let cool for 10 minutes.
Pour the cooled, spiced brown butter into the 36-ounce container.
Add the bottle of whiskey to the spiced brown butter liquid and whisk for about 30 seconds. Save the bottle.
Place the container in the freezer to freeze overnight.
Once the butter fat is frozen completely, remove the container from the freezer. Use the knife to cut into the layer of frozen butter so you can easily remove the “brick” of butter. Set aside for another use or discard. Think shortbread cookies or Victoria sponge cake!
Strain the remaining liquid through the fine-mesh strainer lined with a cotton dish towel, cheese cloth or dinner napkin into another bowl or container. This helps remove all the butter and spice residuals left behind so you have a nice clear brown butter washed whiskey.
Pour the whiskey back into the bottle, cap it, and good to go! You can store in your liquor cabinet or in the freezer.