Scrub the potatoes and plate the wire rack in the bottom of the Instant Pot. Add the water and potatoes to the pot.
Place on the lid, make sure the knob is turned to sealing and select Pressure Cook or Manual for 15 minutes on high. Let the cycle run, do a 5-minute natural release, and then carefully perform a manual release.
Transfer the potatoes to a large bowl, and discard the water. If you want peeled potaotes for your mash, you can peel them when they’re cool to the touch, but I like to leave my skins on for texture.
Add the warm milk and 3 tablespoons of the butter, 1 teaspoon of the salt, and a half teaspoon of the pepper to the potatoes and mash. You can use a ricer or a or an electric mixer if desired, just make sure the milk is warm. This helps with texture. Set the mashed potatoes aside.
Return the pot to the Instant Pot and add the remaining butter. Set it to Saute for 25 minutes on high.
After about 3 minutes, and the butter has melted, add the ground venison to the pot.
Saute until browned, about 5-7 minutes.
Add the onion, carrots, and celery. Cook for an additional 5 minutes, until they start to soften.
Add the garlic, tomato paste, remaining salt, remaining pepper, thyme, and sage. Mix well, letting this sweat for 5 minutes.
Finally, add the beer and let the cycle finish, scraping any bits off of the bottom of the pan for flavor.
Once the cycle has finished, stir in the peas. The hot filling will cook them just enough so that they’re not mushy.
Pour the filling into a 9×13 inch casserole dish. Top with the mashed potaotes and spread into an even later.
Turn the oven to lo broil and place the Shepherd’s Pie on the middle rack of the oven. Broil for 5-7 minutes, checking frequently, until the top is golden and crispy.* Enjoy!
Notes
I like to dump my cooked filling and mashed potatoes into a casserole dish and broil to get a crispy top, but this is optional. You can certainly just spoon the mashed potatoes over the cooked filling in the Instant Pot and call it a day!