Melt chocolate morsels in microwave safe bowl on HIGH for 30 second intervals
until melted, about 1 1/2 minutes total time. Stir until smooth.
Beat 1/2 cup softened butter and 16 ounces brown sugar at medium speed with mixer
about 5 minutes or until well blended.
Add eggs, 1 at a time, just until blended after each addition.
Add melted chocolate, beating just until blended.
Sift together flour, baking soda and salt. Gradually add to chocolate mixture
alternately with sour cream, beginning and ending with flour mixture. Beat at low
speed just until blended after each addition.
Gradually add 1 cup hot water in slow
stead stream, beating at low speed just until blended.
Stir in 2 teaspoons vanilla extract.
Spoon batter evenly into 2 greased and floured aluminum foil lined 9-inch
square, 2-inch deep pans.
Bake at 350 degrees F for 40 minutes or until a wooden pick inserted in center
comes out clean.
Cool in pans on wire racks.
Bring 2 cups brown sugar, whipping cream and 1/2 cup butter to a boil in 3 quart
pan over medium heat, stirring often; boil 1 minute.
Remove from heat; whisk in
powdered sugar and remaining 2 teaspoons vanilla extract.
Add pecans, stirring gently
3 to 5 minutes or until mixture begins to cool and thicken slightly. Pour at once
over cakes in pans.