Cut a loaf of sourdough bread in half vertically so that the two ends are separated. Set one half aside.
Using one half of the loaf, slice the bread in half lengthwise as if you are building a sub sandwich so that there is a top slice and a bottom slice.
Spread the softened butter across each bread piece, using more or less as necessary.
Spread the garlic paste on top of the butter.
Set your oven to broil and put a rack on the top most position. Place the bread either directly on the rack or on a baking sheet and place on the top rack directly under the heating coils. Leave the door slightly open.
Broil the bread until it reaches your desired doneness, approximately 3-5 minutes. Make sure that you are watching the bread as it cooks fast and can easily burn. Immediately remove the bread to a cutting board and cut into slices.
Notes
You can find garlic paste at your local grocery store near the fresh herbs in a tube along with other herbs and pastes.The exact amount of butter and garlic paste that you need will vary with the exact size/shape of your bread.