You can boil the potatoes in water on the stovetop or in the Instant Pot. When the potatoes are done, drain them and put them into the bowl of a stand mixer. Add the butter and salt. Stir the potatoes so the butter distributes evenly. Add the sour cream.
Gradually add the milk, all the while beating. Watch the consistency of the potatoes as you may or may not need all the milk. When the potatoes are completely mixed, turn the mixer to whipping mode and whip them for about 10 seconds. Set the potatoes aside.
Filling
Put butter and ham base in a cast iron skillet and heat the skillet on medium until the butter starts to melt.
Add the onion, carrot, and bell pepper. Sauté until the onion is translucent. Add the garlic and continue to sauté.
When the garlic has softened, but not browned, add the peas and broccoli and move all the vegetables to the sides of the pan and add the ground beef. Break the beef and stir it to completely cook it.
Add the spices to the pan and stir them into the beef. Add the flour and stir.
Put the beef base into a heat-proof measuring cup and add the water, red wine, tomato paste, and Worcestershire sauce. Stir well to combine.
Pour the mixture into the pan and stir until the gravy thickens.
Topping
Spread the potatoes over the filling. If you wish, leave an inch of space all around and fill that space with peas. You can top the mashed potatoes with cheese if you wish.
Bake the casserole in a 350 °F (177 °C) oven for about 30 minutes or until the gravy is bubbling and the top has started to brown.
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