In a large heavy saucepan, bring the broth, milk and salt to a boil. Reduce heat to a gentle boil; slowly whisk in cornmeal. Cook and stir with a wooden spoon for 15-20 minutes or until polenta is thickened and pulls away cleanly from the sides of the pan. Stir in cheese.

Spread into a greased 11-in. x 7-in. baking dish. Cool to room temperature, about 30 minutes. Cut polenta into 16 pieces, then cut each diagonally in half to make 32 triangles; place on a greased baking sheet. Bake at 350° for 12-15 minutes or until light golden brown.

For mushrooms, saute mushrooms in oil and butter until tender. Add the garlic, thyme, salt and pepper; cook 1 minute longer. Add wine and lemon juice; cook and stir until liquid is almost absorbed.

Top each triangle with 1-1/2 teaspoons mushrooms; sprinkle appetizers with cheese. Serve warm. Yield: 32 appetizers.