Combine pecans and 1/4 cup praline liqueur; cover and set aside overnight.
Cream butter; gradually add sugar, beating well. Add vanilla; beat well. Add eggs and milk, beating well.
Combine flour, baking powder, and cinnamon; add to creamed mixture, stirring well. Stir in pecan mixture. Pour batter into 2 greased 7 1/2- x 3- x 2- inch loaf pans. Bake at 325° for 55 minutes or until a wooden pick inserted in center comes out clean. Cool in pans 10 minutes. Remove from pans; place on wire racks to cool completely.
Drizzle 1/4 cup praline liqueur evenly over each cooled loaf. Wrap each loaf in cheesecloth; cover tightly in aluminum foil. Allow to season for 3 days before serving.