1. Heat oven to 350 degrees . Coat two 13 x 9 x 2-inch baking pans with nonstick cooking spray. Line pan bottoms with parchment or wax paper; coat paper with spray.
2. Prepare cake mix according to package directions with oil, eggs and 1 1/3 cups water. Fold in grated carrot. Divide evenly between prepared pans and spread level. Bake at 350 degrees for 18 minutes or until dry to the touch and cakes have pulled slightly away from edges of pans. Cool in pans for 10 minutes, then invert onto wire racks and remove paper.Filling
3. In a medium bowl, beat Neufchatel, 3/4 cup of the cream and 1/4 cup of the sugar until smooth and fluffy. Beat in vanilla extract.
4. In a separate bowl, beat remaining 1/4 cup cream and remaining 1 tsp sugar to medium-stiff peaks.
5. Cut 16 rounds of cake with a 21/2-inch cookie cutter. Cut 8 rounds with a 23/4-inch cutter (keep cuts close together in order to fit). Place one 21/2-inch round into bottom of a jar, compressing with fingers to fit. Spread with 2 tbsp of the cream cheese filling and 2 tsp of the coarsely chopped nuts. Repeat layering with a second 21/2-inch cake layer, 2 tbsp of the cream cheese and 2 tsp of the nuts. Top with one 23/4-inch cake layer. Repeat process in other jars with remaining cake rounds and most of the remaining cream cheese filling and nuts. Fold remaining cream cheese filling (about 1/3 cup) into whipped cream. Top each jar with 2 tbsp of the whipped cream mixture and sprinkle with a few nuts to garnish.