Poke a few holes in each potato using the tines of a fork or knife. Rub with the avocado oil and place on a parchment lined baking sheet. Bake for about 1 hour, turning potatoes halfway through until fork tender. Remove and let rest until cool enough to handle.
Combine the leftover brisket with the 2 tablespoons of BBQ sauce and stir together.
Slice the potatoes down the middle and pinch the ends together to open up the middle of the potatoes.
Fill each potato with equal amount of the wilted spinach, BBQ shredded brisket and top with cheese.
Return to the oven until cheese is melted and bubbly.
Remove and garnish with the tomatoes, red onions and chives. Serve with extra BBQ sauce.