HEAT oven to 350ºF.
MIX butter and cream cheese in large bowl until blended. Add next 4 ingredients; mix well.
POUR into 2-qt. casserole sprayed with cooking spray; top with Cheddar.
BAKE 45 to 50 min. or until knife inserted in center comes out clean.
Add 2 sliced green onions to batter before pouring into prepared casserole.
Prepare using PHILADELPHIA Spicy Jalapeno Cream Cheese Spread.