Line a cookie sheet with parchment paper.
Spread the Macadamia Nuts in a single layer on the sheet and roast at 350 degrees until golden brown (about 10 -15 minutes).
Let nuts cool. Add to a plastic bag and then use a food mallet to crush them.
Combine nuts and simple syrup in a glass bottle or other non-reactive container and let infuse for 2-3 hours.
Strain the Macadamia Nuts with a cheescloth into a clean glass bottle. Add vanilla extract to taste as desired.
Refrigerate and use within 2 weeks.