Add the chopped pata (butter) in to a medium sized pot or pan. Set over medium heat. The butter will now go through a series of stages.
First it will melt, then the milk fats will start to separate – these are the white, floaty bits. Stir occasionally here so nothing sticks to the bottom of the pot.
Keep it on the heat and eventually the butter will start to foam. Stir it a little bit and allow the brown bits to float to the top. It should smell nutty. From here, stir it a little for another 30 seconds or so, so the butter browns further.
Remove from the heat and allow to cool for five minutes.
If you are wanting to have the pata (butter) whipped immediately, fill a large bowl with ice water. Add a smaller bowl in to the water and pour the pata parauri (brown butter) in to it.
Using a spatula, stir to around the bowl to help it cool down. It will start to thicken in to a paste again, now it is ready to whip.
If you are not needing for 40 minutes or so, simply allow the pata (butter) to come to room temperature on the bench. Once it is slightly thick, it is ready to whip as above.