First, start cooking the Yukon Gold Potato (5). Put them in a pot and submerge them in cold water. Bring them to a boil and let them cook until completely tender and mashable for about 25 to 30 minutes.
While the potatoes cook, preheat the oven to 400 degrees F (200 degrees C) and get out a 9-inch pie dish to hold everything. Then it's time to start on the filling.
Heat the Canola Oil (1 dash) in a large skillet over medium high heat. Brown the Ground Beef (1.5 pound) in it while you break it up with a spoon, which should take about 4-5 minutes. Drain off any excess grease.
Add the Carrot (2), Garlic (2 clove), Fresh Rosemary (1 sprig), and Onion (1) and let them soften for a minute while you season the mixture with Salt (1 pinch) and Freshly Ground Black Pepper (1 pinch).
Add the All-Purpose Flour (2 tablespoon) and stir it in to thicken the filling. Lastly, add the Worcestershire Sauce (1 tablespoon) and Guinness® Stout Beer (1 cup). Bring the mixture to a low boil, then reduce it to simmer.
Let the filling simmer for 15-20 minutes to develop loads of flavor and cook off the liquid. Take it off the heat and set it aside.
When the filling is done, the potatoes should be just about done. Take the Butter (1/2 cup), Garlic (1 clove), and Fresh Rosemary (1 sprig) combine them in a microwave-safe bowl. Microwave the mixture to melt the butter for about a minute.
Drain the potatoes and return them to the pot they cooked in. Pour the hot butter mixture all over them and add the Extra Sharp Cheddar Cheese (4 ounce) and Salt (1 pinch). Mash the mixture all together and let it cool for a minute.
Stir in the Egg (1) yolk once it has cooled a bit to make them extra rich. Pack the meat mixture tightly and evenly in the pie dish, pressing it down firmly. Scoop the mashed potatoes on top and smooth them out into an even layer. Be sure to seal the meat mixture in with the potatoes.
Bake the shepherd's pie for about 25 minutes.
Let it cool for a minute. Serve and enjoy!