
In a small bowl, use a fork to mash the 1 tablespoon softened butter together with the flour until it forms a paste; set aside.
In a Dutch oven or similar large, deep pot, melt the remaining 2 tablespoons butter over medium heat. Once melted, add the shallot and cook until it is softened and turning translucent, 1 to 2 minutes. Stir in the garlic and cook 30 seconds.
Add spinach by large handfuls, stirring it so that it cooks down and all fits in the pan—this whole process will take 3 or so minutes and the spinach will cook down to shockingly little.
Stir in the butter flour mixture until incorporated.
Dot the cream cheese over the top. Stir until the cream cheese is nicely blended.
Stir in the salt, pepper, nutmeg, and Parmesan. Taste and adjust the seasoning as desired. Enjoy hot.