Add the egg yolks, lemon juice, salt and mustard powder to a food processor. Blend together until well combined. Crush the ice cubes. You can do this by adding them to a sealable food bag and pounding them with a rolling pin. Add the crushed ice to the food processor and blend into the egg mixture.
Step 2
Carefully drizzle the cold olive oil into the food processor a little at a time. Pulse the mixture as you pour the oil. Continue to blend until all the oil has been incorporated and the mayonnaise has thickened to your desired consistency. You may use avocado oil in place of olive oil if preferred. Please be sure to adjust your macros to reflect any changes made.
Step 3
If the mayonnaise is still a little loose, you can refrigerate it a while before using. This will allow the mixture to thicken further. Once prepared, store the mayonnaise in an airtight container in the fridge until ready to serve.