For the dough, begin by combining the flour, baking powder, baking soda, and salt in a large bowl. In a separate bowl, mix together the oil, aquafaba, water, and vinegar. Pour the wet ingredients into the dry and use a sturdy spatula or wooden spoon to incorporate. Stir until it forms a loose, shaggy dough.

Turn the mixture out onto a lightly floured surface and knead for 5 - 10 minutes, until the dough becomes smooth and supple. Cover with a clean kitchen towel or piece of plastic wrap, and let sit at room temperature for at least an hour before proceeding. Alternately, you could prepare the dough ahead of time and store it in the fridge for up to a day before using. Just let it warm back to room temperature first.

While the dough rests, prepare the fillings. Begin by making master potato dough. Place the potatoes in a large pot and add enough water to cover. Set over medium heat and bring to a boil. Cook the potatoes until fork-tender; about 15 minutes. Thoroughly drain and transfer to a large bowl. Add the vegan butter while still hot to allow it to melt in, along with the aquafaba and salt. Mash thoroughly until smooth and creamy.

Divide the main potato mixture between seven bowls. If you have a kitchen scale to ensure equal measures, this would be an ideal time to break it out.

For the cheesy broccoli filling, finely chop the broccoli before adding it to one of the bowls, followed by the nutritional yeast, vinegar, and pepper. Stir thoroughly to combine.

For the truffled mushroom filling, heat the olive oil in a small saucepan over medium heat. Add the mushrooms and saute until softened and lightly browned around the edges; 5 - 6 minutes. Transfer the cooked mushrooms to another bowl of potato filling. Add in the onion powder and truffle oil, stirring well to incorporate.

For the caramelized onion filling, heat the olive oil in a small saucepan over medium heat. Add the diced onion and garlic and saute for 2 minutes to soften. Add in the vinegar before sprinkling the baking soda evenly over the mixture. Don't be alarmed if it froths lightly. Stir vigorously and reduce the heat to medium low. Cook, stirring every few minutes, for about 15 minutes, until dark amber brown. Transfer to another bowl of the master potato filling and stir well to combine.

For the smoky beet filling, simply add the chopped beets, vinegar, and liquid smoke to a bowl of master potato filling and mash vigorously to combine.

For the spinach filling, add the spinach, garlic powder, and onion powder to another bowl of the master potato filling and mix well to combine.

For the samosa filling, mix together the coconut milk, spices, and lemon juice in a small bowl until smooth. Transfer the mixture to a bowlful of plain master potato filling, followed by the thawed peas, and stir thoroughly to combine.

For the cookie dough filling, add the melted butter, brown sugar, chocolate chips, and vanilla extract to the final bowl of master potato filling. Mix to combine, and once smooth, add in the flour. Stir until completely incorporated.

At last, we're ready to roll! Begin by preheating your oven to 375 degrees. To assemble the knishes, begin by cutting the dough into seven equal pieces. A kitchen scale would be particularly helpful in this situation, too. Lightly flour your work surface and begin rolling one of the balls into a rectangle, as thinly as possible. The exact measure isn't critical, but aim for about 8-inches long by 6-inches wide.

Take one of your fillings and mound it up in a thick line down the center, horizontally. Wrap the pastry dough around it, doubling over if needed, pinching the ends to seal. Cut the log into 4 equal pieces, about 2 inches long each. For each individual piece, pinch and press one of the cut ends in, wrapping it over the filling but still allowing a peephole at the top. Place the open end down on a baking sheet lined with parchment paper or a silicone baking mat, gently pressing it down into a slightly flattened round. Repeat with the remaining dough and fillings, allowing at least an inch between each knish on the baking sheet. You will need two baking sheets to hold them all.

Bake at 375 degrees for 30 - 35 minutes, rotating the baking sheets halfway through until golden brown all over. Let cool for at least 10 minutes before serving. They're best enjoyed hot or warm, but can be delightful at room temperature, too.