Bring a small pot of water to a boil.
Score (make an X-cut) on the top or bottom of the apricots, and carefully drop them into the pot of boiling water. Leave them in the water for about 45 seconds, or until the skin starts to split further.
Remove the fruit from the water, and drop it into a bowl of ice water to cool.
Pull the skin off the apricots, slice them in half, remove the pits and cut them into dice-sized pieces.
Add the diced apricots, maple syrup, tamari and mustard to a small saucepan, and bring it to a boil. Reduce the heat to low, and let the sauce simmer for about 10 minutes, or until it thickens and coats the back of a spoon.
Remove the sauce from the heat, and using an immersion blender, or a regular blender, puree the sauce until it's smooth.
If the sauce doesn't seem thick enough, return it to the pot and simmer it for a few more minutes. It will thicken more as it cools, so be careful to not overcook it.
Brush on chicken, fish, tofu or vegetables as you grill. Store leftover glaze for up to 1 week in an airtight jar.