Slice beef into 1/2 to 3/4 inch strips. Put oil in the Instant Pot and select "sauté". When the oil is hot, brown the mean in batches until all meat is browned -- do not crowd. Transfer meat to a plate when browned. Add the garlic and sauté 1 minute. Add soy sauce, 1/2 cup of water, brown sugar (can be reduced a little), and ginger. Stir to combine. Add browned beef and any accumulated juices. Select "High Pressure". Set timer for 20 minutes. When done, turn Instant Pot off and use the quick pressure release. Combine the cornstarch and 3 tablespoons water, whisking until smooth. Add cornstarch mixture to the sauce in the pot and stir constantly. Select "sauté" and bring to a boil, stirring constantly until the sauce thickens. Stir in the green onions.