Chop garlic and onion finely, grind the black peppers if you use whole ones.
Heat up the pan(medium heat), when it’s hot enough add oil, then add garlic and onion, stir for 30s add ground pepper, stir for 30s more.
Add water, sugar, soy sauce, vegan oyster sauce and plant based milk, when it starts to boil, turn to low heat
Let it simmer for about 5 minutes until it thickens, turn off the heat. You can store it in a clean jar for a week in the fridge.