Roast bananas. Adjust oven rack to upper middle position and heat oven to 325°. Place 3 unpeeled, (bright yellow) bananas on a baking sheet. Bake until skins are completely black, about 20 minutes. Let cool for 5 min.

Make Pudding. Meanwhile, whisk ½ c. sugar, egg yolks, and cornstarch in medium bowl until smooth. Bring half and half, remaining sugar, and salt to simmer over medium heat in large sauce pan. (I prefer to use a dutch oven.) Whisk ½ c. simmering half and half mixture into yolk mixture. (Pour half and half mixture slowly and whisk constantly and quickly. You don’t want your yolks to curdle.) Slowly whisk tempered yolk mixture into saucepan. Cook, whisking constantly, until mixture is thick and large bubbles appear at surface, about 2 minutes. (The bubbles are also referred to as lava bubbles. They will rupture. Be warned.) Remove from heat and stir in butter and vanilla.

Process pudding. Transfer pudding to food processor. Add warm peeled roasted bananas and 2 tbsp. lemon juice, and process until smooth. (Don’t over process. After making this, I would recommend first processing bananas and lemon jiuce, and then adding in pudding. Over processing the pudding breaks down the compounds you just built in the heating process and leads to a thinner consistency.) Scrape into large bowl and place plastic wrap directly on surface of pudding. Refrigerate until slightly cool, about 45 min. (It can stay refrigerated longer if needed.)

Assemble and chill. Cut remaining bananas into ¼" slices and toss in bowl with remaining lemon juice. Spoon one quarter of pudding into a 3-quart trifle dish and top with layer of cookies, layer of sliced bananas, and another layer of cookies. Repeat twice, ending with pudding. Place plastic wrap directly on surface of pudding and refrigerate until wafers have softened, atleast 8 hrs. or up to 2 days. (I followed the same steps but made individual trifles. I ended with cookies instead of pudding, and it softened just fine.)

Top and serve. With electric mixer on medium speed, beat cream, sugar, and vanilla until stiff peaks form, about 2 min. Top banana pudding with whipped cream and serve.