Thin Chocolate Icing
from Betty Crocker Cookbook, 1950 edition

If you are looking for a thin chocolate icing or glaze that will become firm, not sticky, this is an excellent choice.

FMM: I use this recipe for chocolate eclairs and once for Boston Cream Pie. Many website dip chocolate eclairs in Ganache before it cools. Ganache is made with equal parts chocolate and cream. Though equally delicious, ganache is a little different than a chocolate glaze. While a glaze will set up and harden, a "firm" ganache will remain a thick paste at room temperature and only harden when refrigerated.

1 square (1 oz.) unsweetened chocolate
1 tsp. butter
2 T. boiling water
1 cup sifted confectioner's sugar

Melt the chocolate and butter in the top of a double boiler over low heat; stir constantly until just melted. Blend in the boiling water and confectioner's sugar. If you happen to find it too thin, add a little more powdered sugar. If too thick, add more hot water.Do not beat long.

Drizzle while still warm over chocolate eclairs, cream puffs, Boston Cream Pie, etc.

Tip: Use immediately - If the glaze stands too long before use, it will thicken. Keep it covered with plastic wrap if you are not using it immediately. If it thickens, put it over the heat to thin it out again.

The Best Chocolate Glaze
from https://www.allrecipes.com/

This chocolate glaze for cake is rich, decadent, and oh so easy!

6 tablespoons cocoa powder
5 tablespoons butter
1 cup confectioners' sugar
3/4 teaspoon vanilla extract
2 tablespoons hot water, divided

Melt cocoa and butter together in a small saucepan over low heat, stirring until smooth, about 5 minutes. Remove from heat.

Whisk in confectioners' sugar and vanilla extract. Gradually whisk in hot water, 1 teaspoon at a time, until glaze is thick and smooth.

Yield: 3/4 cup