America's Test Kitchen proposes the following recipe as their "Perfect Latin Flan" (pg. 785, The Complete America's Test Kitchen Cookbook 2001-2016):
This recipe should be made at least 1 day before serving. We recommend an 8.5 x 4.5 inch loaf plan for this recipe.
4 2/3 oz sugar
1/4 cup water + 2 tablespoons warm tap water
2 large eggs + 5 large yolks
14 oz sweetened condensed milk
12 oz evaporated milk
1/2 cup whole milk
1 1/2 tablespoons vanilla extract
1/2 teaspoon salt
Stir together sugar and 1/4 cup water in medium heavy saucepan until sugar is completely moistened. Bring to boil over medium-high heat, 3-5 minutes and cook without stirring until mixture begins to turn golden, another 1 to 2 minutes. Gently swirling pan, continue to cook until sugar is the color of peanut butter, 1 to 2 minutes. Remove from heat and swirl pan until sugar is reddish-amber and fragnant, 15-20 seconds. Carefully swirl in 2 tablespoons warm tap water until incorporated; mixture will bubble and steam. Pour caramel into 8.5 x 4.5 inch loaf pan; do not scrape out saucepan. Set loaf pan aside.
Adjust oven rack to middle position and heat oven to 300 degrees. Line bottom of 13 x 9 baking pan with dish towel, folding towel to fit smoothly and set aside. Bring 2 quarts water to boil.
Whisk eggs and yolks until combined. Add sweetened condensed milk, evaporated milk, whole milk, vanilla, and salt, and whisk until incorporated. Strain mixture through fine-mesh strainer into prepared loaf pan.
Cover loaf pan tightly with aluminum foil and place in prepared baking pan. Place baking pan in oven and carefully pour boiling water into pan. Bake until center of custard jiggles slightly when shaken and custard registers 180 degrees, 1.25 to 1.5 hours. Remove foil and leave custard in water bath until loaf pan has cooled to room temperature. Wrap loaf pan tightly with plastic wrap and chill overnight or up to 4 days.
To unmold, slide paring knife around edges of pan. Invert serving platter on top of pan and turn pan and platter over. When flan is released, remove loaf pan. Use rubber spatula to scrape residual caramel onto flan. Slice and serve. Leftover flan may be covered loosely and refrigerated for up to 4 days.
It would seem like the amount of caramel left in the pan if you don't scrape would vary based on the size of the saucepan you use. Why would you not scrape the remaining caramel into the pan? Would it affect the texture/flavor?