Mix the water and lemon slices in a pitcher. Refrigerate for 1 hour.
Prep the ingredients per the instructions above.
Heat the oil in a saute pan on medium heat. Saute shallot and garlic until soft and golden brown. Set aside to cool.
Make the Salisbury: In a large bowl, mix together the ground beef, breadcrumbs, milk, Worcestershire sauce, sauteed shallot and garlic, and season with salt and pepper. Form the meat into oval disks.
Prep potatoes: Peel and cut potatoes into bite-sized chunks so they all cook evenly. Place in a pot with cold water over high heat. Once boiling, turn the heat down to a simmer.
In a saucepan, melt the butter. Once the butter is melted, stir in the cream to warm and then remove from the heat and set aside.
Heat a skillet over medium-high heat. Sear the Salisbury steaks on both sides to brown well. Then remove from the skillet and set aside. Add the oil and butter to the skillet. Saute the mushrooms and thyme until the mushrooms are softened. Stir in the flour until mixed well and cook until golden brown, about 1 to 2 minutes. Stir in the broth until fully combined and add the Salisbury steaks back into the skillet. Bring to a simmer until the gravy builds deep flavor, about 15 to 20 minutes or longer if needed.
Check the potatoes by inserting a fork into them. Once the fork slides in and out with ease, take off the heat and strain out the water.
Make mashed potatoes: Mash the potatoes with a fork or potato ricer. Slowly add in the cream and butter mixture and whip until smooth. Season with salt and pepper to taste. Keep warm until you are ready to serve.
Finish the Salisbury: Once the gravy has built flavor and thickens into a gravy consistency, season with salt and pepper to taste. Remove the thyme before serving.
Toast the bread.
For the peas: Heat the butter in a saute pan over medium heat. Saute the peas until hot. Season with salt and pepper to taste.
To serve: Serve the Salisbury steaks with mashed potatoes. Spoon the mushrooms and some of the gravy over the Salisbury steaks and gravy over the mashed potatoes. Enjoy with peas, bread, and lemon water.