Chop mushrooms in food processor. In large skillet, melt 2 TBS butter over medium high heat and add mushrooms. Cook for 5-8 minutes, or until liquid evaporates. Cool completely. In medium mixing bowl, whisk 1/4 lb butter until slightly whipped. Add the cooled mushrooms and season with pepper. Blend well. Refrigerate or freeze in air-tight container. If frozen, bring to room temperature before using. To freeze, place generous tablespoons of butter on cookie sheet. When frozen, transfer to freezer container. Makes 1 cup.