Place the juniper berries, allspice, kosher salt, peppercorns and fennel seeds in a mortar and pestle and crush to a medium grind.
Sprinkle the venison tenderloins evenly on all sides with the spice mixture and rub it in gently with your fingers or the back of a spoon.
Coat the bottom of an oven-proof frying pan with vegetable oil and place on the stove over medium-high heat.
Lightly sear the tenderloins on all sides (no more than 2 minutes total), then transfer the pan to the oven.
Roast the venison for 7 to 9 minutes, to an internal temperature of 130°F (medium rare). Test after 7 minutes to be sure you don't overcook the meat.
Remove the tenderloins from the oven, tent loosely with foil and let rest for 10 minutes.
While the venison rests, make the sauce.
Melt the butter in a saucepan over medium heat. Whisk in the flour and cook until golden, 1-1/2 to 2 minutes.
Slowly whisk in the hot chicken broth until blended and smooth.
Add the grated gjetost and stir until the cheese has melted and the sauce is smooth.
Whisk in the aquavit and sour cream and continue cooking, stirring occasionally, for 3 to 4 minutes longer.
To serve, carve the venison into 3/8-inch slices, and either transfer to a serving platter or plate individual servings.
Tips for Making This Recipe
The seasonings and sauce in this dish work nicely with pork too, so if venison is not an option for you, you can successfully make it using pork tenderloins instead.Special note: This recipe is adapted from "Kitchen of Light: New Scandinavian Cooking" by Andreas Viestad.