Preheat oven to 350 degrees, and grease a 2 1/2 quart deep oval baking dish.
Peel the apples. Core, and chop into 3/4″ chunks. Spread evenly over the bottom of the baking dish.
Put sugar and molasses in a medium bowl, and mix with hands until evenly colored. Note that this is just making brown sugar. I struggled for years keeping it on hand but not dried out. I gave up, and I just make it as I need it now. And I never measure the molasses… You could just use brown sugar if you have it.
Add the oats, raisins, baking powder, cinnamon, salt, and half of the walnuts, and mix thoroughly.
In a separate bowl, lightly whisk the eggs. Add the milk and vanilla and whisk to combine.
melt the butter.
Add the milk mixture and melted butter to the oat mixture, and mix well. It will seem quite soupy.
Spread the oat/milk mixture evenly over the apples. Sprinkle with the remaining nuts, and bake for about 38 minutes, until the oat custard is set and the top is light brown.
While it’s OK at room temperature, it’s best served warm.