Years ago I worked with a women who made her own Kahlua. While digging around looking for something to make one night, I came across her recipe. It is not as thick as the store-bought one, but just as delish.
4 cups sugar
4 Tablespoons of instant coffee
4 cups of water
a fifth of 100 proof vodka.
1 vanilla bean
Combine all ingredients except for the vodka and boil 40 minutes. Cool. Pour into 2 one-quart bottles. Divide the vodka between the 2 bottles. Split the vanilla bean with a knife and one half in each bottle. Let it stand for 21 days.