In a saucepan, melt butter with sweetened condensed milk over medium-low heat until smooth.

In a bowl, mix together oats, brown sugar, nuts if using.

Stir dry ingredients into wet ingredients until no dry bits remain.

Scoop dough by tablespoons onto a baking sheet. Chill 30 minutes until firm.

Roll dough into balls, then flatten slightly to shape cookies.

Store finished cookies in an airtight container at room temperature. Enjoy!