Cookies and cream marble cake with buttercream icing

Buttercream icing (powdered sugar [sugar, cornstarch], vegetable shortening [palm oil, soybean oil, cottonseed oil, monoglycerides, polysorbate 60], nonfat dry milk, dried egg whites, natural and artificial flavor, salt), sugar, enriched wheat flour (bleached wheat flour, niacin, reduced iron, thiamine mononitrate, riboflavin, folic acid), <span class="allergen">eggs</span>, chocolate & vanilla cake concentrate (bleached wheat flour, cocoa powder [processed with alkali], nonfat dry milk, palm oil, modified food starch [corn], sugar, potassium bicarbonate, dextrose, sodium acid pyrophosphate, salt, <span class="allergen">soy lecithin</span>, soybean oil, <span class="allergen">whey</span>, color [yellow corn meal, spices {turmeric, annatto}], gums [cellulose, guar, xanthan], sodium stearoyl lactylate, cornstarch, natural and artificial flavors, monocalcium phosphate, cinnamon), soybean oil, <span class="allergen">butter</span>, <span class="allergen">egg whites</span> (<span class="allergen">egg whites</span>, guar gum, triethyl citrate), dark chocolate cookie grind (<span class="allergen">wheat flour</span>, sugar, soybean oil, palm oil, cocoa [processed with alkali], invert sugar, contains 2% or less of the following: corn flour, <span class="allergen">soy lecithin</span>, chocolate liquor, cornstarch, salt, baking soda, natural flavor), chocolate sandwich cookie (<span class="allergen">wheat flour</span>, sugar, vegetable shortening [soybean oil, hydrogenated soybean oil], cocoa [processed with alkali], contains 2% or less of the following: cornstarch, molasses, sodium bicarbonate, salt, <span class="allergen">soy lecithin</span>, natural and artificial flavors, ammonium bicarbonate, propylene glycol, ethyl alcohol, caramel color [<span class="allergen">sulfites</span>]), <span class="allergen">soy lecithin</span>, emulsifier (water, mono - and diglycerides, sugar).