Spray mini muffin pans with non-stick spray; set aside.: The tiny pans should feel slick to the touch, ensuring the cakes release cleanly once cooled. When you spray, you may see a fine mist glimmer on the metal; that shine is your insurance against sticking. One common mistake is under greasing the wells, which leads to broken tops when you invert the pans. If you notice the spray pooling, wipe the excess with a paper towel to avoid greasy pockets that affect browning.
Whisk together flour, sugar, salt, and baking soda in a mixing bowl; set aside.: As you whisk, inhale the neutral, slightly dusty scent of the dry mix, and watch for even color so lumps are gone. This step distributes the leavening and salt, so each bite rises uniformly and tastes balanced. An error to avoid is adding wet ingredients before the dry is evenly combined, which can create uneven pockets of soda or salt. If you see clumps after whisking, push the mixture through a sieve or break them apart with the whisk.
Melt butter in a small saucepan over medium heat. Add water and bring to a boil.: You will hear a soft shimmer as the butter melts, and then the mixture will steam as it reaches a boil. This hot liquid helps bloom the dry ingredients for a tender crumb. Be cautious not to over boil, because prolonged high heat can slightly brown the butter and shift the flavor. A frequent misstep is overheating so watch for a steady stream of bubbles rather than an aggressive boil.
Pour hot mixture over dry ingredients and beat with a hand beater till barely blended. Beat in the sour cream, egg, zest, and lemon juice till smooth.: After pouring, you should smell warm butter and citrus as steam rises, and the batter will look glossy. Use the hand beater to bring the dry and wet together until you no longer see dry pockets, but stop before the batter becomes overly smooth; a gentle hand keeps the cakes tender. Then add the sour cream , egg , zest, and lemon juice , which will introduce tang and a silky sheen. A common trap is overbeating after adding the egg, which tightens gluten and yields denser cakes. If the batter becomes gummy, rest it five minutes to relax the texture before scooping.
Scoop batter into muffin pans. Bake at 325° for about 12 minutes. Let cool for 5 minutes, then turn onto cooling racks. Cool completely before glazing.: When you scoop, the batter should hold a slight mound and not run like pancake batter. In the oven you will notice the tops transition from pale to a gentle golden edge, and a toothpick will come out with a few moist crumbs. Cooling five minutes helps the cakes set so they keep their shape when inverted, and fully cooling prevents the glaze from sliding off. A typical mistake is glazing while the cakes are warm, which melts the glaze and makes a runny finish. If you find one cake underbaked, give the rest a minute or two more, watching carefully to avoid drying.
Dip lemon drops top side down into the glaze. Let excess glaze drip off into the bowl, then invert lemon drops bottom side down onto cooling racks. (Place waxed paper underneath the cooling racks for easier clean up.) Let sit till glaze hardens.: As you dip, the glaze should cling and create a thin, glossy coat that dries to a slight sheen. You will hear a soft drip as excess glaze returns to the bowl, and once inverted, the undersides will reveal a tidy, even finish. Place waxed paper under racks to catch drips for easy clean up. Avoid dunking multiple times immediately, because a thick layer can slump and obscure the cake shape. If the glaze seems too thick, thin it slightly with a drop of milk rather than multiple dippings.
Whisk all glaze ingredients together in a small mixing bowl. Heat for about 10 seconds in the microwave till glaze is very thin.: The glaze will start as a powdery paste that becomes glossy as you whisk, and a quick burst in the microwave loosens it so it is pourable. After heating, stir until smooth and watch for a velvety sheen, adding a touch more milk if needed to achieve a thin dipping consistency. Be careful not to overheat, which can make the glaze grainy or separate the butter. A frequent slip is adding too much liquid at once, so add it gradually while whisking to hit the right viscosity.
