Preheat the oven to 350°F / 180°C / Gas Mark 4, no fan.
Process graham crackers in a food processor until crumbs form. Stir the crumbs with melted butter.
Grease a 9x13 inch baking pan (23x33cm) with butter and line it with parchment paper (don't omit this step, the condensed milk sticks very easily to the pan). Greasing the pan with butter helps the parchment paper to stick. Add the cookie crumbs to the pan.
Press the cookie crumbs into the bottom of the pan (I like to use a spoon or a measuring cup to do that).
Sprinkle chocolate chips on top of the crust, then peanut butter chips, followed by roughly chopped nuts, and shredded coconut.
Slowly pour the condensed milk as evenly as possible over the bars.
Bake for about 25 minutes, until golden.
Let cool completely (it will take about an hour) before cutting into 12 squares (otherwise the bars won't hold their shape).
Enjoy!