Combine flour and salt in a 2 quart heavy non-aluminum saucepan. Whisk in reduced-fat milk and next 3 ingredients, whisking until smooth.
Cook over medium heat, whisking constantly, 10-12 minutes or until thickened. Remove from heat. Stir in vanilla.
Fill a large bowl with ice; place pan in ice, and whisk custard occasionally until completely cooled (about 30 minutes).
Spoon 1/2 cup custard into each of 8 (5 oz.) cups or glasses. Top each with 1-2 tablespoons whipped topping, filling completely. Scrape top with a knife to level whipped topping. Garnish with shaved chocolate, chopped chocolate-covered expresso beans, or shortbread cookies.
To make ahead, pour cooled custard into a gallon-size zip lock bag, gently pressing out excess air. Seal bag and chill up to 24 hours. To serve, snip off a corner of bag and pipe into serving cups.