Mix the salt and sugar together.
In a non-reactive dish (Pyrex), lay half of the rosemary, black peppercorns, and juniper berries on the bottom, followed by half of the salt and sugar mixture.
Lay the venison filet on top of the mixture.
Lay the remaining rosemary and juniper berries on top of the venison, followed by the rest of the salt and sugar.
The venison should be fully covered. If not, simply make more of the salt-and-sugar mixture, using a 40:60 salt-to-sugar ratio.
Cover with plastic wrap and place in the refrigerator for three days.
Remove the venison from the mixture and rise under cold water and dry very well.
Sprinkle the venison with ground black pepper on both sides. For a more robust flavor, dust with a little ground juniper as well. Slice thinly and enjoy. If not eating immediately, wrap in plastic wrap and refrigerate until needed. It will last up to a week in the refrigerator.