In a heavy-bottom saucepan, combine sweetened condensed milk, white chocolate, unsalted butter, pistachio paste, vanilla extract, and a pinch of salt. Cook over medium-low heat while stirring constantly for 12-15 minutes.

Once thickened, transfer the mixture to a greased dish, spread evenly, and let cool at room temperature for about 30 minutes before refrigerating for at least 2 hours.

Preheat oven to 325°F (160°C). Mix crushed digestive biscuits or graham crackers with melted butter and sugar. Press into mini cups or baking dish and bake for 7-8 minutes.

Lightly butter your hands, scoop the chilled brigadeiro mixture, and roll into bite-sized balls. Coat in finely chopped pistachios and press onto cooled cookie bases if using.

Refrigerate the brigadeiros for at least 30 minutes to firm up before serving.