In a pan, combine brown sugar, sugar and water. Cook over medium high heat until mixture comes to a boil. Reduce heat and simmer 5 minute.
Place pecans and vanilla beans in a 1 gallon jar.
Pour hot mixture into jar and cool. Add vodka and stir well. Cover tightly and store in a dark place at room temperature at least 2 weeks.
Shake jar gently once daily. Pour mixture through a wire mesh strainer lined with 2 layers of cheesecloth into a bowl, discarding solids.
Pour mixture through a wire mesh strainer lined with a coffee filter into a bowl. Change filter often. Mixture will drip slowly.
Pour mixture into jars; cover tightly. Store at room temperature.
Makes about 4 1/2 cups liqueur.
Store at room temperature