Set the butter in a frying pan over low-medium heat. Cook as it melts, then begins to sputter. Once the butter goes silent, and is foaming, stir to brown it evenly. When you see lots of brown bits at the bottom, immediately remove from heat and pour into a bowl, scraping the brown bits into the bowl. Let cool for a bit so that the brown bits (milk solids) sink to the bottom. Once they do, you can separate the golden liquid from the brown butter bits.

Add the brown butter bits, brown sugar, egg yolks, heavy cream, and salt to a pot. If you are using the milk, add it now too (if you’re using buttermilk it goes in later).

Slice open the vanilla bean(s) and add them and the scrapings to the pot. Whisk to combine.

Set the pot over medium-low heat and cook, stirring often until the temperature reaches 165 F. You’ll see the custard thicken slightly at the bottom at this point.

Set a mesh sieve (not a very fine sieve, we want most of the brown butter to escape) over a heatproof bowl and pour the custard through it. It might catch some of the brown butter bits (that’s ok) and any egg bits that cooked too quickly (we don’t want those!).

Pour in the buttermilk and whisk to combine.

Remove the vanilla beans from the sieve and add them back to the custard.

Let the mix come to room temperature then cover with plastic wrap and set in the fridge overnight. If your ice cream maker requires you to freezer the bowl, set it in the freezer now too.

Preheat the oven to 350 F. Line a small, greased cookie sheet with parchment paper.

Spread the flour over the pan in an even layer.

Bake the flour for about 7 minutes. (This is done to kill any bacteria.) Let cool completely.

Whisk together the softened butter and sugar very well. Add the salt and vanilla and whisk to combine.

Add the sweetened condensed milk and whisk well.

Add the cooled flour (shake it to remove it all from the pan) and chocolate chips and stir to combine.

Scoop teaspoons of the cookie dough onto the pan that had the flour until you have lots of little bits. Set the tray in the freezer until you’re ready to churn the ice cream.

Churn the ice cream

The custard may have separated a bit as it chilled (you might see some butter at the top), give it a quick whisk to mix.

Pour into prepared ice cream machine and churn according to manufacturer's instructions.

Store the ice cream in an airtight container and freeze. It’ll be ready to eat after freezing for about 4 hours.

Straight out of the freezer (after a long freeze) the ice cream might be hard to scoop, leave it at room temperature for 5 minutes and it’ll be smooth.