This comforting cottage pie is packed with a slow-cooked beef filling, root vegetables, and red wine, then topped with cheesy Dubliner mashed potatoes and baked until golden brown. It takes just 30 minutes of prep and makes 10 servings, making it perfect for a St. Patrick's Day celebration.
Add the oil to a large rondeau pot over medium high heat.
Place in the ground beef and cook on all sides to sear it until browned and cooked throughout, which takes about 6 to 7 minutes. Stir this frequently.
Set the beef to the side on a plate and then add the onions and leeks to the pot with the rendered meat fat and caramelize the onions over low to medium heat for up to 45 minutes or until very well browned, sweet, and tender.
Next, add in the carrots, celeriac root, and turnips and sauté for 5 to 6 minutes over medium heat just until very lightly browned.
Stir in the garlic and cook it just until it becomes fragrant, which takes about 30 to 45 seconds.
Add back in the beef to the pan and stir it until combined.
Deglaze with the red wine and cook it until au sec or almost gone, which takes about 3 to 4 minutes.
Stir in the tomato paste until the ingredients are coated.
Next, sprinkle in the flour and stir it to combine.
Pour in the beef stock and cook for 1 to 2 minutes or just until thick.
Season with Worcestershire sauce, Dijon mustard, salt, pepper, and thyme. Adjust any seasonings and stirring these in and tasting it. If you like Dijon mustard go with the full 2 tablespoons.
Transfer the beef filling to a deep 13x9 pan. Briefly set it aside.
In a large pot of boiling salted water add in the potatoes and cook for 12 to 13 minutes or until tender.
Drain the potatoes and hand mash them or run them through a food mill until smooth.
Fold in the buttermilk, melted butter, 1 cup of cheese, egg yolks, salt, and ground white pepper until mixed on. Transfer to optional piping bag with a large star or round tip.
Add the potatoes to the top of the pan with the beef filling in any design you want. You can do stars, zig sags, fleurettes, or even just add to the top and smooth it out.
Garnish with a ¼ cup of melted butter and ½ cup of cheese. Bake at 350° for 25 to 30 minutes or until lightly browned on top.
Sprinkle on an optional garnish of chopped parsley and serve.
Notes
The biggest difference between a good cottage pie and a great one is the 45 minutes you spend caramelizing those onions. I know it seems like a long time, but that slow, low heat brings out a sweetness that you cannot get any other way. The rest of the recipe builds on that foundation, and if you skip it, the filling will taste flat.White pepper for the potatoes: I use ground white pepper instead of black to keep the mashed potatoes looking clean and white. It is just an aesthetic thing I was taught in culinary school, but it makes a difference in presentation.Freeze before or after baking: This cottage pie freezes well either way. If baking from frozen, go at 350 degrees for 60 to 75 minutes. If thawed in the fridge overnight first, bake at 350 for 35 to 40 minutes.Potato consistency: The potatoes should be creamy and smooth but stiff enough to stand upright when piped or scooped. If they are too thick, add a little more buttermilk or melted butter until you get the right texture.Cut the recipe in half: If you are cooking for a smaller group, this recipe scales down easily. Use a regular 9 inch pie dish instead of the 13x9.Make-Ahead: This recipe is meant to be eaten immediately; however, keep it warm in the oven covered in foil at low temperatures for up to 1 hour before serving.How to Store: Cover and place it in the refrigerator for up to 4 days. This will freeze covered for up to 2 months. Thaw in the refrigerator for 1 day before reheating.How to Reheat: If you reheat the cottage pie, place it in the oven at 350° for 10-15 minutes or until warmed. When heating up a single portion, I recommend warming it in the microwave.