Heat 1 tbsp oil in a large frying pan over medium-high heat. Add one-third of the beef and cook, turning occasionally, for 3 minutes or until browned. Repeat in 2 more batches, adding a little more oil as needed. Transfer beef to the pressure cooker.
Heat the remaining oil in the pan over medium heat. Add the onion and cook, stirring, for 4 minutes, or until lightly browned. Add the flour and tomato paste, and cook, stirring, for 1 minute.
Gradually add the stock, scraping the base of the pan, until evenly combined. Stir in the diced tomato. Add the potato, carrot and bay leaf to the pressure cooker. Pour in the stock mixture and stir to combine.
For a stove-top pressure cooker, secure the lid and heat over medium-high heat until the valve begins to hiss, then reduce heat to low and cook for 25 minutes. Release the pressure slowly (see notes).
Season and sprinkle with parsley, if using. Serve with crusty bread to mop up the sauce.
