Put the minced beef on a bowl and add the salt,black pepper(pleas fresh ground black pepper!),cumin and mixed with your hands ( I like to add some thyme and paprika....but it's your call) Split it in 4 balls and shaped like a burger
Meanwhile spread some butter on the buns and toast them(only on the inside)
At the end finely chop the endives and add them to the bottom bun and cover with a little bit of the sauce(s) and the rest on the top bun.
Construct it as you like! And serve! If you like you can put everything on a couple of trays or dishes and have a DYS burger party
I like to use the red endives because they have some spice or heat.