Combine cocoa,butterand oil in top of double boiler over hot,not boiling;stir over low heat untill butter has melted.Remove from heat;stir in sugar.Add eggs and vanilla just untill well combined.Stir flour into mixture just untill blended. Pour batter into ungreased 9-inch square and arrange pecan halves evenly on top.Place pan with batter in 13x9 pan; place both in oven. Pour hot water to depth of 1 inch into the 13x9 inch pan. Bake at 350 degrees for 40-45 minutes until knife inserted 1/2 inch from edge comes out clean and brownie-like crust has formed; do not over bake. Remove from water bath; let cool on wire rack until warm. Scoop onto serving plates and top with your favorite ice cream or chill; cut into squares and serve with sweetened whipped cream.