In a large non-stick skillet, whisk the condensed milk and cocoa powder together until obtaining a homogeneous mixture (without lumps of cocoa powder). Then, stir in the melted butter.
Cook mixture over medium-low to medium heat (large burner), stirring constantly, until the mixture thickens and starts to peel away or show the bottom of the pan when you scrape it with your wood spoon (about 10-15 minutes).
The chocolate fudge mixture should be thick enough to show you the bottom of the pan for a couple of seconds before the mixture levels out again. Mix in the vanilla extract if desired.
Remove pan from the heat, add the chopped cookies, and mix them together with a wooden spoon until cookies are completely mixed in the chocolate fudge mixture.
Line a 8 x 8-inch pan with a greased sheet of heavy duty aluminum or with plastic wrap, allowing it to overlap 2 opposite sides.
Place mixture into the lined pan and smooth the top with a spatula, making sure mixture is level. Cover and refrigerate for at least 12 hours or until set. Right before serving, lift the foil or plastic, place on a flat surface, cut into squares or rectangles, and sift powdered sugar on top of each bar. This is the traditional treat.
If you would like to top them with chocolate ganache and berries instead of powdered sugar, place the chocolate chips and heavy cream in a microwavable bowl and microwave on medium power for about 1 minute.
Stir together well and microwave again until chocolate has melted. Whisk well until obtaining a smooth mixture/ganache. Spread chocolate ganache on top of the fudge and cookie bars (without the powdered sugar), place raspberries on top, drizzle melted white chocolate, and refrigerate until ganache is set.