Preheat oven to 350°F. Place flour on a parchment-lined baking sheet and bake for 7 minutes to kill any bacteria. Remove flour and allow it to cool completely.
Cream butter and sugar together with an electric mixer until light and fluffy, about 3-5 minutes.
Add condensed milk, vanilla extract, and salt and beat for another minute. Gradually beat in cooled flour until just combined. If mixture is too crumbly add another tablespoon condensed milk. Fold in the sprinkles if using.
Scoop out into a bowl and serve. You can place in the fridge for 30 minutes for a firmer texture.
Notes
Brown the butter ahead of time if you like a slightly nutty flavor.
Take the time to beat together the butter and sugar, otherwise you will have a grainy dough.
Let the flour cool before adding to the dough.
Speaking of the flour, sometimes it forms chunks when baked so you can sift to remove the chunks of flour.
If you want bites, use a small cookie scoop and roll into balls.