Strawberries in a Milk Chocolate Stout

I made a strawberry milk chocolate stout by adding 4 lbs of strawberries to the last 10 mins. of the boil in a 5 gallon batch.

I just took a sampling and the strawberry taste is minimal, if any.

Any ideas on how best to add the strawberry flavoring into the beer?

Perhaps I could just pitch in some in carboy for about a week and to circumvent wild yeast issues, first boil those strawberries down?

Or, do the same, yet add them into the bottling bucket and let it sit for a few minutes before bottling?

Thanks

There are a couple of options..

1. Fresh Strawberries in Secondary
2. Frozen Strawberries in Secondary (what I would do)
3. Strawberry Extract