Cut onion and lemon in half (leave a little onion skin on for tannin) and place in bottom of IP.
Add stock.
Generously salt and pepper each lamb shank and add on top of onion and lemon.
Top with thyme.
Set IP to manual 60 minutes.
Time release 20 minutes.
Remove shanks and place on baking sheet with sides.
Broil in oven when ready to serve.
Remove the broth and strain into hot roux to make the gravy.
