Mix together condensed milk, half and half, eggs and vanilla in blender or with a mixer.
Melt together butter and brown sugar. Pour into a 9 X 2 round pan or small jello mold. (Double the recipe for larger mold such as a Bundt pan.) Pour pudding mixture on top of sugar mixture. Place pan or mold in a larger pan of water and bake at 325 degrees for an hour and 15 minutes.
Turn over on to serving plate when taken out of oven.
You can use whole milk or 2% milk if you want a lighter dessert.
To make flavored milk:
Combine milk, peppercorns, bay leaves and cloves in small saucepan. Warm over medium heat until hot but not boiling.
Remove from heat, cover, and let sit for 20 minutes.
Strain into small bowl or measuring cup, set aside. Discard solids.
To make béchamel sauce:
Melt 1 tbsp butter in a saucepan over medium heat.
Whisk in flour; cook for 1 minute, whisking constantly.
Gradually whisk in milk mixture. Whisk another 3 minutes until sauce thickens.
Stir in salt, white pepper, nutmeg, and half-and-half. Set aside, covered.
To finish the dish:
Heat remaining butter and a splash of olive oil in a large skillet over medium heat.
Add onion, saute until tender, about 5 minutes.
Add 1/2 bag of spinach; cover skillet momentarily until leaves wilt.
Add the other half bag. Turn with tongs until all leaves are wilted.
Pour sauce over spinach, stir to combine. Serve.