French Shepherd's Pie (Hachis Parmentier) Made With Ground Beef

2 Tbsp Duck Fat Could substitute with butter
1 Large Onion, Diced
4 Large Cloves Garlic, Pressed
2 Pounds Lean Ground Beef
1 Pound Ground Sausage You can adjust the final flavor of your dish based on the type of sausage you add. I enjoy "Mild Italian" sausage for this dish.
Salt/Pepper
2 Cups Sturdy Red Wine Cabernet works well.
5 Large Carrots, Peeled and Sliced
2 tsp Tomato Paste
3 Tbsp Fresh Parsley, Flat Leaf, Chopped
1 tsp Fresh Thyme, Chopped
1/2 Cup Flour
2 Cups Beef Stock

Melt Duck Fat to a medium stock pot. Add the diced Onion. Sauté until translucent.
Add pressed Garlic Cloves. Sauté for a minute to bring out the aromatics.
Add the Ground Beef and Ground Sausage. Sauté until browned. Skim off some of the fat that has risen to the top, taking care to leave a few tablespoons (which will act with the added flour to create a Roux for thickening). Season with Salt and Pepper.
While meat is browning, slice the Carrots and chop the Parsley.
Add Red Wine. Cook on medium heat until the wine has reduced to basically nothing.
Add Carrots, Parsley, Thyme, and Tomato Paste. Cook over medium heat until the Carrots start to soften.
Sprinkle the Flour over top of mixture. Stir to coat the meat and vegetables. Cook and stir for one minute.
Pour in the Beef Stock and stir until it thickens. Turn heat down to low and continue to cook until it is even thicker, and is the right consistency to act as the bottom layer of your Shepherd's Pie.
At this point, you can either spoon your meat base into the baking dish, or pop the pot into the refrigerator for a few hours, or overnight. By doing this, the flavors will meld and become more intense.

Preheat oven to 400℉.
Wash Potatoes and place into large saucepan. Cover with generously salted cold water. Set over medium high heat until boiling. Once boiling, boil for 20 minutes, or until they are tender enough to easily be pierced with a knife.
Drain and cool the Potatoes to a temperature that you are able to handle, yet still quite warm.
Peel and cut potatoes in batches into a food mill. Mash potatoes through the food mill into a large bowl. (Using a food mill or ricer will produce fluffier potatoes, vs. an electric mixer, which will create more "elastic" potatoes.)
Add Butter, grated Cheese, Sour Cream, Milk, and Salt/Pepper. Stir to combine.
Spoon the potatoes over the meat mixture. Use an offset spatula to press/spread potatoes evenly over the meat mixture.
Melt Butter and brush over top of the potatoes. Sprinkle with the grated Parmesan.
Place on a lined baking sheet to catch any spill over. Bake for 30 minutes, or until the filling is bubbling steadily and the potatoes have developed a golden brown crust.
Remove from oven and let rest for 10-15 minutes before cutting and serving. Enjoy!