START: On a 6-quart Instant Pot, select Normal/Medium Sauté. Add 1 tablespoon of butter and let melt. Add the rice and garlic, then cook, stirring, until the grains are translucent at the edges, 1 to 2 minutes. Stir in the sausage and 2 1/2 cups water, scraping up any bits stuck to the bottom of the pot, then distribute the mixture in an even layer.
Fast: Press Cancel, lock the lid in place and move the pressure valve to Sealing. Select Pressure Cook or Manual; adjust the pressure level to Low. Set the cooking time for 3 minutes. When pressure cooking is complete, quick-release the steam by moving the pressure valve to Venting. Press Cancel, then carefully open the pot.
FINISH: Vigorously stir in the Parmesan, 1 teaspoon pepper and the remaining 4 tablespoons butter, adding the butter one piece at a time. Add the arugula and stir until slightly wilted, about 30 seconds. Taste and season with salt, then stir in the vinegar. Serve sprin-kled with pepper and with additional Parmesan on the side.