Prepare a baking sheet by lining it with parchment paper.
In a medium saucepan, combine the sugars, evaporated milk, and butter. Cook over medium heat, stirring constantly, until the mixture reaches soft-ball stage at 238°F.
Remove the saucepan from heat and stir in the pecans and vanilla extract.
Quickly but carefully, spoon the praline mixture onto the prepared baking sheet, creating small mounds.
Let the pralines cool completely at room temperature until they harden.
Notes
Store pralines in an airtight container at room temperature for up to two weeks.