Lightly grease a stainless steel pan with butter spray.
In a large bowl, whisk eggs, milk, sugar and vanilla.
Cut each bread slice into 6 pieces. Dip each piece in the milk custard and line it in the greased pan. Repeat by placing custard-soaked bread pieces snugly next to each other to form a layer.
Scatter a handful of berries on top.
Repeat above 2 steps for another layer of bread and berries. Note - It can be 2, 3 or 4 layers of bread and berries depending on the size of your bowl.
Pour the leftover custard on top. Cut the butter into small pieces and layer them on top along with the remaining berries.
Gently cover the bowl with a paper towel. Using a piece of aluminum foil, cover the paper towel and gently secure the paper towel around the rim of the stainless steel bowl.
Add 1 cup of water in the Instant Pot. Place the cake pan on the trivet. Gently put the trivet in the pot. Close Instant Pot lid with pressure valve to sealing.
Pressure Cook (Hi) and adjust the cook time to 20 minutes. Allow 10 minutes of natural pressure release.
Open the Instant Pot and carefully lift the trivet with the pan, and take it out.
Serve with fresh berries and powdered sugar or your favorite ice-cream.
Notes
If using glass bowls, add extra 5 minutes of pressure cook time.