Back to basics: Revel (Oatmeal Fudge) Bars

Revel Bars and I go way back. The original was on a recipe card from Toll House i think, and ever since i was 10 or 12 i have been making them; there was a time that pans of these were flying out the door by the dozen as holiday orders. High school and college friends made these one of my signatures, and the aroma of them baking gives me flashbacks to the 80's and 90's. (Scrunchies are back with a vengeance, so there! May we never see the high teased bangs again though.)

This recipe has survived the food-snobbery of side-eyeing anything using canned milk, and has been improved by using good chocolate and a judicious amount of salt. Quick-cooking oats create the best texture; old-fashioned or steel-cut hydrate differently and don't make a satisfying layer.
For this post I decided to go full flashback and make them as I first did, with a hand mixer and countertop toaster/oven. Obviously a "serious" mixer makes quicker, handier work of the oatmeal base, but they taste the same regardless.

Revel Bars -- 1 10x15 pan
1 stick/8 oz/228 g butter or   margarine (one case where there's   no marked difference), divided       into 7 oz (200 g) and 1 oz (28 g)
2 cups/14 oz/400 g brown sugar
2 eggs
2 1/2 cups/11 oz/ 325 g all-purpose flour
3 cups/9 oz/260 g. quick-cooking oats (oatmeal)
1/2 tsp/2.5 g salt
1/2 tsp/2.5 g baking soda
1 14 ounce/400 g can sweetened condensed milk
12 ounces/340 g good-quality bittersweet chocolate
2 tsp vanilla extract

Line a 10x15 rectangular pan with foil or parchment. Preheat the oven to 350F/170C.
For the oatmeal base: Put the 7 oz/200g butter in a mixer bowl. Add the brown sugar to the mixer bowl and cream together until fluffy and light. Beat in the eggs until smooth, then the dry ingredients. Mix on medium speed to a thick batter.
For the fudge: Put the 1 oz/28g butter, condensed milk and chocolate in a microwave-safe bowl or measuring cup. Microwave on full power in 30-second bursts, stirring each time, until just melted. Add the vanilla and stir smooth.
Using your hands and an offset spatula, press 2/3 of the oatmeal base into your prepped pan. Spread the fudge on the oatmeal base, covering it completely. Dot the remaining oatmeal base by the spoonful on top of the fudge layer, spacing evenly.
Bake about 25-30 minutes until the oatmeal part is lightly browned and doesn't hold a dent when you press a fingertip in. Cool on a rack, then carefully lift the slab out of the pan using the parchment or foil onto a cutting board. Cut into 24-30 bars with a serrated knife. 
These taste best warm but not hot, an hour or two out of the oven. To get that texture after, microwave a bar approximately 8 seconds on high power.

Half the batch fits in a 9x9 square pan; check after 15 minutes. Cut in 12-16 bars.