Heat garlic in 1 1/2 teaspoons olive oil in a skillet over medium-high heat until golden; remove from pan. Add spinach, stirring until wilted; remove from pan. Add 1 1/2 teaspoons olive oil to pan; swirl. Add polenta slices; cook 3 minutes on each side. Bring a large skillet filled with water to a simmer. Break eggs gently into pan; cook 3 minutes. Remove with a slotted spoon. Blend 1 poached egg yolk, mayonnaise, lemon juice, 2 teaspoons water, melted butter, and salt in a blender. Top each polenta slice with 1/4 cup spinach, 1 egg, 1 1/2 tablespoons sauce, and garlic.