Pour oil in a large stockpot.

Place over medium heat.

When oil is hot and shimmering, add onions, carrot and garlic cloves. Sauté until browned.

Add whole black pepper, brown sugar and ginger. Cook until melted.

Add sherry. Cook and reduce for 30 seconds to 1 minute.

Add water, soy sauce and pineapple juice. Bring to a boil.

Add sugar. Stirring, bring to a boil.

In a small bowl, mix cornstarch and water until smooth.

While sauce is boiling, add cornstarch mixture, whisking until well combined. Let boil for 3 - 4 minutes.

Remove from heat. Allow to cool slightly.

Strain sauce into a storage container. Discard solids.

Store in a tightly sealed container, in the refrigerator, until ready to serve, up to a month.