2 Tablespoons flour
1½ – 2 Tablespoons cold water
2 cups whole milk
½ cup granulated sugar
1 large egg
1 Tablespoon butter
1 teaspoon vanilla extract
In a small bowl, whisk together flour and water to form a slurry; set aside.
In a medium saucepan over medium heat, whisk together milk and sugar. Heat to a simmer, whisking occasionally. In a small, separate bowl, beat egg until well blended. Take the hot whisk from the milk mixture and whisk the egg mixture. Move the whisk back and forth between these two mixtures 3-4 times in order to temper the eggs to prevent them from curdling. Slowly pour tempered egg into the hot milk and sugar, whisking constantly. Add the slurry. Cook over medium heat until it reaches the thickness desired. Remove from heat and stir in vanilla and butter. Cool.
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