Combine garlic, peppers, and parsley. Make thin slits in roast with knife (or use larding needle) and stuff mixture into slits. S&P roast.
In heavy dutch oven over med/high heat, melt shortening and brown roast on all sides until a little crusty.
Remove roast, lower heat to medium, add vegetables and saute for 10 minutes.
Pour broth into the pot, a little at a time, while scraping the bits of browned drippings from the bottom and sides until the pot is fairly clean.
Put roast back in pot with the vegetables, pour the remaining broth over and add enough water to bring the liquid level to about an inch from the top of the roast and add 1 t salt.
Bring to a boil, reduce to simmer and simmer for 1 1/2 hours. Best reheated and served the next day.
The following is optional:
Remove roast and store in fridge. Remove carrots from broth and reserve to garnish roast or serve on the side. Strain broth (not too fine), discard remaining solids and store broth in airtight container in fridge.
Next day, remove solidified shortening from top of broth and discard. Put broth and roast back in pot and slowly bring to serving temperature on stovetop. When almost to temperature, use some of the broth in a separate pan to make gravy.