2 3/4 pounds plum or Roma tomatoes (about 9 or 10)
1/4 cup extra-virgin olive oil
4 medium shallots, peeled and finely diced
2 cups Arborio, Carnaroli, or Vialone Nano rice
1 cup dry vermouth or dry white wine, at room temperature
2 tablespoons unsalted butter
3 cloves garlic, peeled and grated
2 teaspoons kosher salt
1/4 teaspoon freshly ground white pepper
1/2 cup finely grated Parmesan cheese
1/4 cup mascarpone cheese (optional)
Using the large holes of a box grater set over a large bowl, or a food processor fitted with a grating blade, grate the whole tomatoes. (You should have about 4 to 4 1/4 cups of tomato pulp, seeds, and juice.) Discard the peels.
If using an electric pressure cooker, heat it to its brown or sauté setting (whichever is hotter). If using a stovetop pressure cooker, place the uncovered pot over medium heat. Add the oil and heat until it just begins to shimmer. Add the shallots, mix well, and cook until softened and the edges begin to brown, 3 to 4 minutes.
Add the rice, mix well to coat, and cook until lightly toasted, 2 to 3 minutes. Add the grated tomatoes, vermouth or wine, butter, garlic, salt, and pepper; mix well; and cook 1 minute.
Cover the pressure cooker and lock the lid. Bring up to pressure. Cook on LOW pressure for 7 minutes for al dente, and 8 minutes for softer rice.
Turn off the heat if using a stovetop pressure cooker. Depressurize according to the manufacturer's instructions. Remove the lid. If using a stovetop pressure cooker, return it to medium heat. If using an electric pressure cooker, turn on to WARM.
Mix the risotto to combine. Add the Parmesan cheese and mix until completely incorporated and creamy. Add the mascarpone, if using, and mix until completely combined and heated through. Serve immediately.