Preheat your oven to 180C/350F. Grease the bottom and sides of your dish with some of the butter.
Butter your bread slices lightly with the rest of the butter and spread a thin layer of jam on top of each slice. Arrange half of the slices in a layer on the bottom of your dish. Sprinkle half of the walnut pieces on top. Add the second layer of bread slices and sprinkle with the rest of the walnuts.
In a large mixing bowl, combine eggs, cream, jam, salt and vanilla. Mix really well.
Add 3 cups of the milk and mix again.
Pour the mixture evenly over the bread layers. Add a little more milk if necessary so it just covers the bread layers (up to 1/2 cup).
Bake for 25-30 minutes until the custard has set and the top is golden brown.
Sprinkle with strawberry halves. Serve hot or warm.
Notes
This sourdough casserole can be assembled the night before and kept refrigerated to be baked in the morning for an easy breakfast.This casserole makes it easy to use up any old sourdough bread you may have. If your bread is a bit hard, consider leaving the assembled casserole for 15-30 minutes on your countertop before putting it into the oven. Sitting in the custard sauce will soften old, hard bread.Any leftovers can be easily reheated in the oven. Simply drizzle with a little milk and cover with foil (or place in a lidded ovenproof dish) and reheat at 180C/350F for about 15 minutes.Try a different kind of berries and berry jam in this recipe - raspberries, blackberries or blueberies would all make a delicious version of this French toast casserole.